#include <stdio.h>

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

int fac(int n) {
    int res;
    printf("begin n = %d\n", n);
    if (n==0)
        res=1;
    else
        res=n*fac(n-1);
    printf("eind n = %d\n", n);
    printf("res = %d\n", res);
    return res;
}