#include <stdio.h>

int main() {
    int fac(int n);
    printf("3! = %d\n", fac(3));
    getchar();
    return 0;
}

int fac(int n) {
    int i, res;
    res=1;
    for (i=1; i<=n; i=i+1) 
        res=res*i;
    return res;
}