#include <stdio.h>

int combi(int n, int r){
    if (r == 0)
        return 1;
    else if(n == r)
        return 1;
    else if (r == 1)
        return n;
    else
        return combi(n - 1, r - 1) + combi(n - 1, r);
}
int main(void){
    int n, r;
    n = 4, r = 2;
    printf("C(n=%d, r=%d) = %d\n", n, r, combi(n, r));
    return 0;
}