#include <stdio.h>
int ackermann(int m, int n) {
    if (m == 0) {
        return n + 1;
    } else if (m > 0 && n == 0) {
        return ackermann(m-1, 1);
    } else if (m > 0 && n > 0) {
        return ackermann(m-1, ackermann(m, n-1));
    } else {
        return 0;
    }
}
int main(void) {
    int m = 4, n = 2;
    printf ("Ackermann(%d,%d): ", m, n);
    printf ("%d\n", ackermann(m, n));
    return 0;
}