#include <stdio.h>

/* factorial */
int fact(int n){
    if(n == 0){
        return 1;
    } else {
        return n * fact(n-1);
    }
}

/* combination */
int comb(int n, int r){
    if(n == r){
        return 1;
    }
    if(r >= n){
        printf("please enter n > r > 0 \n");
        return 0;
    }

    return fact(n) / (fact(r) * fact(n-r));
}

int main(){
    // test case 1, di bawah 12
    printf("case 1 = %d\n", comb(8, 4));

    // test case 2, di atas 12
    printf("case 2 = %\n", comb(17,13));

    return 0;
}