#include <iostream>

#include <algorithm>

#include <cstdio>

#define LL __int64

using namespace std;

LL N,M;

LL myc(LL n,LL r){

	LL sum=1;

	for(LL i=1;i<=r;i++)

	sum=sum*(n-r+i)/i;

	return sum;

}

int main(){

	while(scanf("%d%d",&N,&M),N||M){

		LL ans=myc(N,M);

		printf("%I64d things taken %I64d at a time is %I64d exactly.\n",N,M,ans);

	}

	return 0;

}