#include <stdio.h>
// Combination
int f(int n, int r);

int main(void){
    int n, m;
    printf("組合せの数nCrを入力");
    scanf("%d%d", &n, &m);
    printf("%d\n", f(n, m));
}

int f(int n, int r){
    if( r == n )
        return 1;

    else if ( r == 1)
        return n;

    else
        return f(n -1, r -1) + f(n-1, r);
}