>>> TONIGHT, THE MAJOR RAMP-UP AND THE MISSION TO CLEAR THAT COLLAPSED BRIDGE IN BALTIMORE. THE LARGEST CRANE ON THE EAST COAST NOW JOINING THE OPERATION. THE MASSIVE MECHANICAL ARM CAPABLE OF LIFTING UP TO 1,000 TONS ARRIVING FOR ONE OF THE BIGGEST SALVAGE OPERATIONS EVER. PLUS, A FLEET OF TUGBOATS, BARGES, COAST GUARD VESSELS, AND ADDITIONAL CRANES ON THE WAY. ONE OF THE FIRST MAJOR TASKS, CUTTING THAT BRIDGE INTO PIECES TO MAKE IT EASIER TO REMOVE. FOUR WORKERS MISSING AND PRESUMED DEAD IN THE WATER AS OFFICIALS RACE TO RE-OPEN THAT BUSY PORT. >>> ALSO TONIGHT, THE ATMOSPHERIC RIVER STORMS SLAMMING THE WEST THIS HOLIDAY WEEKEND. WE'RE TRACKING IT ALL. >>> THE VIOLENT CHAOS IN HAITI. THE RARE INTERVIEW WITH THE COUNTRY'S MOST INFAMOUS GANG LEADER. WHAT HE SAYS IT WILL TAKE TO GET HIM TO THE TABLE FOR CEASE-FIRE TALKS. >>> THREE PRESIDENTS ON ONE STAGE. INSIDE JOE BIDEN'S FUND-RAISER WITH BARACK OBAMA AND BILL CLINTON. THE RECORD-BREAKING HAUL. >>> AND FORMER PRESIDENT TRUMP, HIS NEW ATTEMPT TO KICK FANI WILLIS OFF THAT GEORGIA ELECTION CASE. >>> THE MYSTER PARTON CLASSIC. WHY SOME FANS SAY IT'S HER BEST ALBUM YET. >> Announcer: THIS IS "NBC NIGHTLY NEWS" WITH LESTER HOLT. >>> AND GOOD EVENING. I'M TOM LLAMAS IN FOR LESTER TONIGHT. >>> IT WILL BE LENGTHY, COMPLICATED, AND DANGEROUS AS WORK BEGINS TO CLEAR WRECKAGE OF THE FRANCIS SCOTT KEY BRIDGE AND THE MASSIVE SHIP THAT CRASHED INTO IT. TONIGHT, A HUGE FLOATING CRANE -- YOU SEE IT RIGHT HERE. IT'S ARRIVED ON THE SCENE. IT'S THE LARGEST ON THE EAST COAST, PART OF AN ARMADA OF BARGES, SALVAGE VESSELS, AND TUGBOATS ON THE WAY. A GOOD PART OF THAT BRIDGE WILL HAVE TO BE SAWED INTO PIECES, SO IT CAN BE LIFTED OFF THE SHIP AND OUT OF THE WATER. ONLY THEN WILL SHIP TRAFFIC RETURN TO THIS PART OF BALTIMORE HARBOR, WHICH WE OBSERVED HOURS AFTER THE DEADLY COLLISION. IT WILL TAKE WEEKS, EVEN MONTHS. PRESIDENT BIDEN WILL VISIT THE SITE NEXT WEEK AS INVESTIGATORS LOOK AT ISSUES ON THE SHIP AND THE BRIDGE THAT MAY HAVE CONTRIBUTED TO THE DISASTER, AND IT'S WHERE WE BEGIN TONIGHT WITH NBC'S TOM COSTELLO. >> Reporter: ARRIVING AT THE SITE OF BALTIMORE'S BRIDGE COLLAPSE, THE BIGGEST FLOATING CRANE ON THE EAST COAST ABLE TO LIFT A THOUSAND TONS FOR ONE OF THE BIGGEST SALVAGE MISSIONS EVER, JUST PART OF A FLOTILLA NOW EN ROUTE INCLUDING THE CRANE THAT LIFTED THE MIRACLE ON THE HUDSON PLANE OUT OF THE RIVER. IN ALL, SEVEN FLOATING CRANES, TEN TUGBOATS, NINE BARGES, EIGHT SALVAGE VESSELS, AND FIVE COAST GUARD BOATS. 8,000 LOCAL JOBS ARE WAITING. >> WE NEED TO CLEAR THE CHANNEL AND OPEN THE VESSEL TRAFFIC TO THE PORT, BECAUSE THE HEALTH OF THE MARYLAND ECONOMY AND THE NATIONAL ECONOMY DEPEND ON IT. >> Reporter: ON THE WATER, THE ARMY CORPS OF ENGINEERS IS USING UNDERWATER DRONES AND SONAR TO MAP THE PRECISE LOCATION OF THE WRECKAGE THEN LAY OUT A COORDINATED SALVAGE PLAN FOR DIVERS. >> HOW WE CAN CUT IT UP INTO THE PIECES WE NEED TO BE ABLE TO LIFT. >> Reporter: NTSB INVESTIGATORS STILL INTERVIEWING CREW MEMBERS AND GATHERING EVIDENCE ON THE CRUSHED CARGO SHIP NOW TRAPPED UNDER THE WEIGHT OF TWISTED STEEL. A PIECE OF HIGHWAY LYING ON TOP. SO, TAKE A LOOK AT THE FRONT OF THE SHIP, AT THE BOW OF THE SHIP, AND YOU SEE THAT PIECE OF STEEL THAT'S LYING ACROSS IT. THAT'S 3,000 TO 4,000 TONS. THAT IS SO HEAVY, IT'S PUSHING THE BOW INTO THE WATER DOWN INTO THE BOTTOM OF THE RIVER, AND THEN IT'S LIFTING THE STERN UP OUT OF THE WATER. BELOW THE WATER LINE, THE RIVER DEPTH IS ROUGHLY 50 FEET. TO RE-OPEN THE PORT, THE CRANES WILL LIFT MASSIVE CHUNKS OF STEEL, CONCRETE, AND SUNKEN CARGO CONTAINERS, SOME HAZARDOUS. ALL OF IT MUST BE GONE. THE SAND ON THE BOTTOM COMPLETELY CLEAN. >> YOU CAN'T LEAVE ANY CONCRETE, ANY STEEL, BECAUSE IT'S A THREAT TO THE VESSEL. WE'LL GET IT ALL OFF THE BOTTOM AND RE-OPEN THE CHANNEL SO IT PROVIDES FOR SAFE NAVIGATION. >> Reporter: MEANWHILE IN HONDURAS CONSTRUCTION WORKER MAYNOR YASSIR SUAZO SANDOVAL'S FAMILY IN A HARD WAIT FOR HIS BODY. HIS BROTHER SAYING, WE ARE STILL WAITING WITH FAITH AND HOPE THAT THEY WILL FIND HIS BODY SO WE CAN BRING HIM HOME. >> AND WITH THAT, TOM COSTELLO JOINS US LIVE TONIGHT. STILL FOUR VICTIMS UNACCOUNTED FOR. LOST UNDERNEATH THAT WATER, AND WE SEE THERE RIGHT BEHIND YOU THAT MASSIVE 1,000-TON POUND CRANE THEY'RE HOPING WILL HELP IN THE RECOVERY? >> Reporter: YEAH, IT'S PRE-POSITIONED. IT'S READY TO GO, JUST PART OF THE MANY SHIPS AND BOATS AND OPERATORS THAT ARE COMING IN. PRESIDENT BIDEN WILL BE HERE NEXT WEEK MEETING WITH INCIDENT COMMANDERS, WE EXPECT, AND THE GOVERNMENT HAS NOW PLEDGED TO MARYLAND $60 MILLION TO HELP IN THE REBUILDING PROCESS. THAT WILL BE A DROP IN THE BUCKET OF WHAT COULD BE A MULTIBILLION DOLLAR PRICE TAG, TOM. >> YEAH, THEY'RE GOING TO NEED A LOT MORE THAN THAT. ALL RIGHT. TOM COSTELLO LEADING US OFF TONIGHT. TOM, WE THANK YOU. >>> HERE IN NEW YORK, THREE PRESIDENTS HELPED BRING IN A $26 MILLION HAUL FOR THE BIDEN CAMPAIGN AT THAT STAR-STUDDED FUND-RAISER, AND IT HAD FORMER PRESIDENT TRUMP FIRING BACK TODAY. HERE'S KELLY O'DONNELL. >> Reporter: WITH A DRAMATIC FLOURISH, THREE PRESIDENTS EMERGED. DEMOCRATIC DONORS POSTED THEIR IMAGES OF THIS ENTRANCE AT A GLITZY NEW YORK CITY FUND-RAISER. NEEDLING A FOURTH PRESIDENT, DONALD TRUMP, WITH A TWIST ON THE SENSITIVE ISSUE OF AGE. IN THIS CLIP RELEASED BY THE BIDEN CAMPAIGN. >> OF ALL THE THINGS HE'S DOING ARE SO OLD, SPEAKING OF OLD. [ LAUGHTER ] AND, YOU KNOW, A LITTLE OLD AND OUT OF SHAPE ANYWAY. [ LAUGHTER ] >> Reporter: TAPPING INTO THE POLITICAL SKILLS OF BILL CLINTON AND BARACK OBAMA TO SELL THE BIDEN AGENDA. DEMOCRATS LOOKING FOR A COUNTERPOINT TO POLLING THAT SHOWS VOTER FRUSTRATIONS WITH PRESIDENT BIDEN. >> YOU'VE GOT RECORD-BREAKING JOB GROWTH. YOU'VE GOT AN UNEMPLOYMENT RATE THAT IS AS LOW AS IT HAS BEEN. FOR AFRICAN AMERICANS, BY THE WAY, THE LOWEST ON RECORD EVER. >> Reporter: TICKETS STARTED AT $250 BUT DONATIONS SOARED AS HIGH AS $500,000 FOR STAR-STUDDED NIGHT. THE EVENT RAISED $26 MILLION. WHILE OUTSIDE, A LARGE AND LOUD PROTEST OVER PRESIDENT BIDEN'S POLICY ON THE ISRAEL-HAMAS WAR. MEANWHILE, FORMER PRESIDENT TRUMP CREATED HIS OWN CONTRAST JOINING MOURNERS GRIEVING NYPD OFFICER JONATHAN DILLER WHO WAS SHOT AND KILLED. THE SUSPECT, A REPEAT OFFENDER. MR. TRUMP SLAMMING PRESIDENT BIDEN FOR NOT DIRECTLY REACHING OUT TO THE DILLERS. >> THEY COULD HAVE CALLED. YOU DON'T HAVE TO BE A ROCKET SCIENTIST TO KNOW EVEN A CALL WOULD BE PERHAPS -- I'M NOT SURE THEY'D TAKE HIS CALL. >> Reporter: AND NEW IN THE GEORGIA ELECTION INTERFERENCE CASE, MR. TRUMP'S LAWYERS ARE ASKING AN APPEALS COURT TO REMOVE FULTON COUNTY D.A. FANI WILLIS AND TO DISMISS THE CASE. TOM. >> KELLY O'DONNELL WITH THAT NEW REPORTING FROM THE WHITE HOUSE. KELLY, THANK YOU. >>> WE NOW GO TO HAITI WHERE TONIGHT THE NOTORIOUS GANG LEADER WHO MANY SAY IS IN CHARGE OF THE CAPITAL SAT DOWN FOR AN INTERVIEW WITH OUR PARTNERS AT SKY NEWS. HIS DEMAND THAT GANGSTERS BE ALLOWED TO JOIN THE NEW GOVERNMENT. HERE'S ELLISON BARBER. >> Reporter: GUNFIRE, ARSON. THIS IS LIFE IN HAITI'S CAPITAL CITY. THE COUNTRY'S NATIONAL POLICE UNABLE TO MATCH THE FIREPOWER OF GANGS. JIMMY "BARBECUE" CHERIZIEN, IS ARGUABLY THE FACE OF HAITI'S GANG WARS. HE CONTROLS LARGE SWATHS OF TERRITORY AND HEADS THE POWERFUL G-9 GROUP, AN ALLIANCE AND ONE OF THE BIGGEST GANGS. IN AN INTERVIEW WITH SKY NEWS' STUART RAMSAY, HE SAYS HE IS WILLING TO CONSIDER A CEASE-FIRE, BUT SEEMED TO SUGGEST THE NEWLY FORMED TRANSITIONAL PRESIDENTIAL COUNCIL MUST INCLUDE GANG LEADERS. [ SPEAKING IN A GLOBAL LANGUAGE ] >> Reporter: IN NORTHERN HAITI, THAT DIVIDE IS EVIDENT. WHAT WE KEEP HEARING FROM PEOPLE IS THAT ONE OF THE BIG CONCERNS IN AREAS OUTSIDE OF PORT-AU-PRINCE IS LESS THE VIOLENCE AND LESS SO WORRY ABOUT THE GANGS AND MORE RIGHT NOW THE CONCERN IS ABOUT HOW THEY DO THINGS LIKE THIS, WASH THEIR CLOTHES, HOW THEY GET FOOD, HOW THEY GET CLEAN WATER. >> IT'S HARD RIGHT NOW TO GET EVERYTHING. >> Reporter: EARLIER THIS WEEK, THE BIDEN ADMINISTRATION APPROVED A PROPOSAL TO SEND HAITI'S POLICE $10 MILLION WORTH OF WEAPONS, AMMUNITION, BULLETPROOF VESTS AND HELMETS ALL FROM THE DEPARTMENT OF HOMELAND SECURITY STOCKPILE, BUT TO MANY IT HAS NOT COME SOON ENOUGH. ELLISON BARBER, NBC NEWS. >>> AND IN THE MIDDLE EAST, DOZENS ARE REPORTED DEAD IN SYRIA TONIGHT AFTER AN APPARENT AIR STRIKE BY ISRAEL, RAISING FEARS OF A WIDER CONFLICT IN THE REGION. NBC'S RAF SANCHEZ IS IN ISRAEL TONIGHT. RAF, WHAT MORE DO WE KNOW? >> Reporter: TOM, THIS IS THE LARGEST APPARENT ISRAELI ATTACK IN SYRIA IN YEARS ACCORDING TO A WAR MONITORING GROUP. THEY SAY THIS STRIKE IN ALEPPO KILLED NOT JUST 36 SYRIAN SOLDIERS, BUT ALSO 6 MILITANTS FROM THE IRANIAN-BACKED GROUP HEZBOLLAH. NOW, ISRAEL IS NOT CLAIMING RESPONSIBILITY FOR THIS STRIKE, BUT, REMEMBER, HEZBOLLAH DOMINATES SOUTHERN LEBANON. THEY ARE ALIGNED WITH HAMAS, BUT THEY ARE LARGER, AND THEY ARE MORE POWERFUL, AND EARLIER TODAY, ISRAEL SAYS IT KILLED A SENIOR HEZBOLLAH COMMANDER RESPONSIBLE FOR ROCKET ATTACKS ON ISRAELI CIVILIANS. THE MILITANTS ARE CONFIRMING HIS DEATH, AND THEY ARE VOWING REVENGE, AND ALL OF THIS IS RAISING FEARS THAT WITHOUT A CEASE-FIRE DEAL, THIS WAR COULD SPREAD WELL BEYOND GAZA. TOM. >> RAF SANCHEZ FOR US, RAF. THANK YOU FOR THAT. >>> BACK HERE AT HOME AN ATMOSPHERIC RIVER IS TAKING AIM AT THE WEST COAST THIS HOLIDAY WEEKEND. 21 MILLION PEOPLE UNDER FLOOD ALERTS FROM SOUTHERN CALIFORNIA INCLUDING L.A. AND SAN DIEGO AS STORMS PUSH THROUGH TONIGHT AND TOMORROW. AREAS IN THE MOUNTAINS COULD SEE UP TO TWO FEET OF SNOW. >>> NOW, TO OUR RARE INTERVIEW WITH THE CIA'S TOP CYBERSECURITY OFFICIAL SPEAKING OUT ON ELECTION INTERFERENCE, TIKTOK, AND YOUR PASSWORDS. SHE SAT DOWN WITH COURTNEY KUBE. >> WHAT WOULD YOU SAY IS THE FOREIGN GOVERNMENT THAT IS, I GUESS, CAUSING YOU THE MOST HEARTBURN RIGHT NOW? >> OH, GOSH, I HEARD SOMEBODY MAKE A GREAT ANALOGY. THEY SAID, RUSSIA AND PUTIN RIGHT NOW ARE LIKE A MASSIVE HURRICANE THAT CAN HAVE SOME VERY LONG-LASTING DAMAGE AND IMPACT, BUT THE PEOPLE'S REPUBLIC OF CHINA AND THE THREAT OF CONFLICT IN THE FAR EAST IS LIKE CLIMATE CHANGE, THE POTENTIAL FOR EPICAL -- LIKE, AN EPIC EVENT THAT COULD REALLY CHANGE LIVES. >> Reporter: JULIEANE GALLINA'S TITLE MAY SOUND BUREAUCRATIC. >> I'M DEPUTY DIRECTOR OF THE CIA FOR DIGITAL INNOVATION. >> Reporter: BUT HER PORTFOLIO IS BROAD AND ESSENTIAL. APPOINTED IN FEBRUARY SHE'S IN CHARGE OF THE CIA'S EFFORTS TO DETECT AND PROTECT AGAINST CYBERTHREATS FROM ABROAD. AMONG HER FOREMOST CONCERN, THREATS TO U.S. ELECTIONS, PARTICULARLY RUSSIA SPREADING FALSE INFORMATION CREATING DOUBT AND SWAYING U.S. OFFICIALS. AND WITH CHINA SHE SEES EFFORTS TO INFLUENCE U.S. OPINION AS THE BIGGEST THREAT. >> IF YOU'RE CHANGING THE MINDS OF A GROUP OF PEOPLE OR MANY PEOPLE, THAT'S HARD TO UNDO. IT'S HARD TO EVEN KNOW WHAT THE SOURCE WAS OR HOW IT HAPPENED. >> Reporter: INCLUDING ON SOCIAL MEDIA. ARE YOU ON TIKTOK? >> NO. >> Reporter: NEITHER ARE HER KIDS OR HER PARENTS, SHE SAYS. >> I TELL THEM, DON'T TOUCH IT. >> Reporter: TIKTOK DENIES BEING OWNED BY THE CHINESE GOVERNMENT, BUT BACK AT CIA HEADQUARTERS, HER BIGGEST CONCERN MIGHT SURPRISE YOU. >> HONESTLY, THE THING THAT CONCERNS ME THE MOST IS WORRYING THAT MAYBE SOMEONE IN MY ENTERPRISE STILL HAS PASSWORD 123 AS THE PASSWORD. YOU KNOW, IN OTHER WORDS, BASIC CYBERHYGIENE. >> Reporter: COURTNEY KUBE, NBC NEWS, LANGLEY, VIRGINIA. >>> AND WE ARE MARKING A TROUBLING ANNIVERSARY TONIGHT. ONE YEAR SINCE "WALL STREET JOURNAL" REPORTER EVAN GERSHKOVICH WAS DETAINED IN RUSSIA. HERE'S ANDREA MITCHELL. >> Reporter: ON TODAY'S FIRST ANNIVERSARY OF EVAN GERSHKOVICH'S ARREST IN RUSSIA, "THE WALL STREET JOURNAL'S" FRONT PAGE WAS MOSTLY BLANK, WHITE COLUMNS WHERE HIS REPORTING SHOULD HAVE BEEN AND A SEARING STORY ON WHAT EVAN HAS LOST DURING A YEAR IN JAIL. >> JOURNALISM IS NOT A CRIME. >> Reporter: PROMINENT JOURNALISTS GATHERED AT THE "WALL STREET JOURNAL" FOR A 24-HOUR READ-A-THON OF HIS WORK. A LONG TIME FOR HIS PARENTS. >> DO YOU THINK THEY'RE DOING ENOUGH? >> WE KNOW THEY'RE WORKING HARD, AND WE JUST WANT THEM TO CONTINUE. >> Reporter: LAST MONTH THE POSSIBILITY OF A TRADE WAS RAISED BETWEEN PRESIDENT BIDEN AND GERMAN CHANCELLOR OLAF SCHOLZ. TO SOURCES TELL NBC SCHOLZ CONSIDERED GIVING UP A RUSSIAN ASSASSIN PUTIN WANTS IN EXCHANGE FOR ALEXEI NAVALNY. THE U.S. WANTED THE DEAL TO ALSO INCLUDE EVAN AND PAUL WHELAN, AN AMERICAN BUSINESSMAN IMPRISONED FOR WHAT THE U.S. SAY ARE FALSE ESPIONAGE CHARGES. A WEEK LATER NAVALNY DIED, THE SOURCES SAY, BEFORE THE TRADE WAS PROPOSED TO THE KREMLIN. TODAY PRESIDENT BIDEN'S MESSAGE FOR EVAN AND HIS FAMILY. >> I ADMIRE THE HELL OUT OF HIM. WE'RE TRYING EVERYTHING WE CAN SO FAR. WE'RE NOT GOING TO GIVE UP. >> DID YOU EVER THINK IT WOULD LAST THIS LONG? >> WE KNEW IT WAS GOING TO BE A MARATHON, BUT STILL HAD HOPES THAT IT WOULD BE SOONER. >> Reporter: TONIGHT CONGRESS HAS FOUR LEADERS IN A RARE BIPARTISAN STATEMENT SAYING, REPORTERS ARE NOT BARGAINING CHIPS AND CALLING ON THE KREMLIN TO RELEASE EVAN AND ALL WHO ARE WRONGFULLY DETAINED. TOM. >> AND TONIGHT WE ARE ALL THINKING ABOUT EVAN AND HIS FAMILY. ALL RIGHT, ANDREA, THANK YOU. >>> IN JUST 60 SECONDS, THE MYSTERY IN THE WATERS OF SOUTH FLORIDA. WHY ARE BIG FISH SPINNING UNCONTROLLAB >>> ALL RIGHT. WE'RE BACK NOW WITH A BAFFLING UNDERWATER MYSTERY. SCIENTISTS ARE TRYING TO FIGURE OUT THE STRANGE PHENOMENON IMPACTING FISH IN THE FLORIDA KEYS CAUSING THEM TO SPIN OUT OF CONTROL AND THEN WASH UP DEAD. HERE'S MARISSA PARRA. >> Reporter: IN THE SHIMMERING BLUE WATERS OF THE FLORIDA KEYS, LONG THE JEWEL OF THAT'S SOUTHERN COAST, A MYSTERY LURKS BENEATH THE SURFACE. FISH WITH THE SPINS, FLIPPING AND SPINNING WITHOUT STOP. >> IN MY LIFETIME OF DIVES, I'VE NEVER SEEN ANY BEHAVIOR FROM FISH LIKE THIS AT ALL. >> Reporter: THIS DIVER FIRST OBSERVED IT LAST YEAR AND SOON LEARNED THE FISH, INCLUDING THESE SMALL TOOTH SAWFISH WHICH CAN GROW UP TO 16 FEET WERE DYING. SCIENTISTS ARE STRUGGLING TO UNDERSTAND WHY. >> IT'S UNPRECEDENTED. THEY DO NOT SPIN LIKE THIS. THEY DO NOT BEHAVE LIKE THIS. THIS IS NOT NORMAL BEHAVIOR AT ALL. >> Reporter: THAT HIGHLY UNUSUAL BEHAVIOR HAS BEEN SEEN IN MORE THAN 40 SPECIES ACCORDING TO FISH AND WILDLIFE. IT HAS REVEALED NO SIGN OF A PATHOGEN OR BACTERIAL INFECTION. OXYGEN LEVELS, WATER SALINITY, pH AND TEMPERATURE ARE NOT BELIEVED TO BE THE CAUSE BEWILDERING RESEARCHERS. >> IT'S A MYSTERY. THERE'S SO MANY DIFFERENT POSSIBILITIES, THAT IT'S REALLY DIFFICULT TO ISOLATE WHICH ONE IT COULD BE. >> Reporter: 28 SAWFISH HAVE BEEN FOUND DEAD, BUT THE ACTUAL NUMBER BELIEVED TO BE HIGHER. A BLOW TO THIS SPECIES EARLY ON ITS ROAD TO RECOVERY. >> SO, TO SEE THESE ANIMALS DYING COULD BE A MAJOR SETBACK. WE WANT TO GET TO THE BOTTOM OF IT AND FIGURE OUT A WAY, A WAY TO COME BACK FROM THIS. >> Reporter: FISHERIES IN THE FLORIDA KEYS REMAIN OPEN, THOUGH STATE OFFICIALS SAY SWIMMING WHERE DEAD FISH ARE OBSERVED ISN'T RECOMMENDED. WHY DO WE NEED TO PROTECT THE ECOSYSTEM AND THE FISH THAT LIVE HERE? >> IT'S VERY SPECIAL. FUTURE GENERATIONS NEED TO BE ABLE TO APPRECIATE IT THE SAME WAY I DID. >> Reporter: MARISSA PARRA, N