> /****************************************************
> 
> 
> 用64可以这样写
> ****************************************************/
> 
> #include<iostream>
> using namespace std;
> 
> 
>  __int64 kin_Cnk(int n,int k){
> 	__int64 sum1 = 1;
> 	__int64 sum2 = 1;
> 	int time = k;
> 	while(time--){
> 	   sum1 *= n--;
> 	   if(sum1%k==0){
> 		   sum1 /= k--;
> 	   }
> 	} 
> 	while(k)
> 		sum2 *= k--; 
> 	return sum1 / sum2;
> }
> 
> int main()
> {
> int n,k,temp;
> __int64 sum;
> while(scanf("%d%d",&n,&k)){
>    if(!n && !k) break;
>    if(k> n/2) temp = n - k;
>    else temp = k;
>    sum = kin_Cnk(n,temp);
>    printf("%d things taken %d at a time is %I64d exactly.\n"
> 			,n,k,sum);
> }
> return 0;
> }
>