http://www.jungol.co.kr/bbs/board.php?bo_table=pbank&wr_id=589&sca=99&sfl=wr_hit&stx=1309 JUNGOL www.jungol.co.kr #include typedef unsigned long long u64; int N; u64 ans = 1; int main() { scanf("%d", &N); while (N) { if (N == 1) printf("1! = 1\n"); else printf("%d! = %d * %d!\n", N, N, N - 1); ans *= N--; } printf("%lld\n", ans); return 0; }