#include <stdio.h>

#define N 10

/* calculates a factorial recursively */
int fact(int x) {
    if (x == 0) {
        return 1;
    } else {
        return x * fact(x - 1);
    }
}

// main function
int main() {
    for (int i = 0; i <= N; i++) {
        printf("%d! = %d\n", i, fact(i));
    }

    fact(5);
    fact('A');

    return 0;
}