#include <stdio.h>
#include <stdlib.h>

int f(int, int);

int main(int argc, char *argv[])
{
  printf("%d\n", f(atoi(argv[1]), atoi(argv[2])));
  return 0;
}

int f(int N, int k)
  {
    if ((k < 0) || (k > N)) return 0;
    if (N == 0) return 1;
    return f(N-1, k) + f(N-1, k-1);
  }