Gaurav Raja can't explain how he memorized such a big slice of pi. The 15-year-old from Salem, Va., insists that there is no trick to memorizing 10,980 digits of pi, a feat that makes him the North American record-holder. He just did it. "I don't see anything in my head. It's just kind of there," he said yesterday. "It just flows, I guess." Gaurav has become a mathematical legend despite being a rising senior at Salem High School.