/*
 * compute factorial using loop
 */
#include <stdio.h>

long fac(long n) {
	long work = 1;
	for (int i = n; i > 0; --i) {
		work *= i;
	}
	return work;
}

int main(void) {
	long n;
	printf("enter n to compute factorial of\n");
	if (scanf("%ld", &n) == 1) {
		printf("%ld! is %ld\n", n, fac(n));
	}
	else {
		printf("not number\n");
		return 1;
	}
	return 0;
}