/*
 * Program to compute factorial using recursion.
 */
#include <stdio.h>

long fac(int a);

int main(void) {

	int n;
	printf("enter n\n");
	if (scanf("%d", &n) != 1) {
		printf("not number\n");
		return 1;
	}
	printf("fac(%d) is %ld\n", n, fac(n));

	return 0;
}

long fac(int a) {
	if (a <= 0)
		return 1;
	else
		return a * fac(a-1);
}