public class ZuHe {
 
  public static void main(String args[]){
   
   
   System.out.print(comm(5,2));
   
  }
  
  static int comm(int n,int k){
   
   if (n==k||k==0)
    return 1;
   else return comm(n-1,k)+comm(n-1,k-1);
   
  }
  
 }