UVA 568 (暑假-数论 -C - Just the Facts)

#include <cstdio>

int main() {
	int n;
	while (scanf("%d",&n) != EOF) {
		int sum = 1;
		for (int i = 1; i <= n; i++) {
			sum *= i; 
			while (sum % 10 == 0) {
				sum /= 10;
			}
			sum %= 100000;
		}
		printf("%5d -> %d\n", n, sum % 10);
	}
	return 0;
}