The largest wrestling tournament in the world started on Saturday at the FargoDome in Fargo, N.D. on Saturday, July 19, with the start of the Cadet National Greco-Roman Championships.     The top 15- and 16-year-old wrestlers in the United States started their competition, although things got going a little bit late. A technical issue with a new computer program to help run the tournament caused the postponement of the 9:00 a.m. session back to 1:00 p.m. Tournament officials ran a single session through about 7:25 p.m. to help catch up on the lost time.    A pair of 2002 Cadet National Greco-Roman champions returned this year in an attempt to repeat: Henry Cejudo of Arizona at 105 pounds and Troy Nickerson of New York at 112 pounds. Both wrestlers won Cadet National titles at a lower weight division last year, with Cejudo at 91 pounds and Nickerson at 105 pounds.    Cejudo won his first three matches with dominance, scoring a pin and a pair of technical falls. He pinned Tyler Jensen of Iowa in 51 seconds, then added 10-0 technical falls over Feuchy Vang of Minnesota and Mike Wilson of Ohio. He had a bye in the fourth round.    Nickerson also started out with four straight victories, all technical falls. He stopped Mike Degliobizzi of Delaware and Carson Sweat of Utah with 10-0 scores, then topped Brad Gruezke of Louisiana 12-0. His final match was a 10-0 technical fall over Jeremy Ensley of Idaho.    A pair of Greco-Roman runners-up from last year were also in the field: Tim McGoldrick of Pennsylvania at 135 pounds and Kyle Bounds of Washington at 145 pounds. Both won their first four bouts handily. McGoldrick scored three straight technical falls then an 8-4 decision while Bounds won by a pin, two technical falls and a 9-1 decision.    Pat McCaffrey of Pennsylvania, who was third in the Cadet Nationals in Greco-Roman last year and was also Cadet National freestyle champion, scored a pair of technical fall wins at 91 pounds.    The Cadet Greco-Roman tournament returns on Sunday, with another session starting at 3:00 p.m.    Teams were also busy registering for the Junior Greco-Roman tournament, which is set to begin on Sunday morning at 9:00 a.m.    Four returning champions who are registered to compete in the Junior Greco-Roman event are Tanner Gardner of Kansas, Angel Cejudo of Arizona, Cheney Haight of Utah and J.D. Bergman of Ohio.    At least a dozen 2002 Cadet National Greco-Roman champions are entered in this year's Junior National Tournament. They include Cory Fish of Washington, Nick Gallick of Arizona, Jeff Schell of Pennsylvania, Dustin Schlatter of Ohio, Jason Johnstone of Ohio, Brent Metcalfe of Michigan, Danny Grater of Kansas, Rocky Cozart of Florida, Nate Matousek of Minnesota, Andy Lowther of Ohio, Kurt Brenner of Pennsylvania and Dallon Norton of Utah.