poj1306 combinations

#include <cstdlib>
#include <algorithm>
#include <cstring>
#include <cctype> 
using namespace std;
typedef unsigned long long ll;
ll C[105][105];
ll (){
    ll x=0;char c=getchar();
    while(c<'0'||c>'9')c=getchar();
    while(c>='0'&&c<='9')x=x*10+c-'0',c=getchar();
    return x; 
}
void build(){
    for(ll i=0;i<=100;i++)
        C[i][0]=1;
    for(ll i=1;i<=100;i++)
        for(ll j=1;j<=i;j++)
            C[i][j]=C[i-1][j]+C[i-1][j-1];
} 
int main(){
    build();
    ll u,v;
    for(;;){
        u=read(),v=read();
        if(!u&&!v)return 0;
        printf("%llu things taken %llu at a time is %llu exactly.n",u,v,C[u][v]);
    }
    return 0;
}