#include <iostream>
#include <vector>
#include<string>
#include<malloc.h>
#include<algorithm>
#include<math.h>
using namespace std;

int recursion(int n){
	if(n == 1){
		return 1;
	}
	return n*recursion(n-1);
}

int main(){
	int n,r;
	while(cin>>n>>r && (n!=0 || r!=0)){
		int sum = 1;
		int j = 0;
		if(n == r || r == 0){
			cout<<1<<endl;
			continue;
		}else if(r>n){
			cout<<"error!"<<endl;
			continue;
		}else{
			for(int i = n,j = 0; j < r; j++){
				sum *= i; 
				i--;
			}
			int rs = recursion(r);
			int res = sum/rs;
			cout<<res<<endl;
		}
	}
}