poj 2249 Binomial Showdown

#include<iostream>#include<cstdlib>#include<cstdio>#include<cstring>#include<algorithm>#include<cmath>using namespace std;__int64 a[ 100000000];int main(){    __int64 m , n ;    while ( scanf("%I64d%I64d",&m,&n), m || n )    {        a[0]=1;        if ( n > m / 2 ) n = m - n ;        for ( int i = 1; i <= n ; i ++ ) a[i] = a[i-1] * ( m - i + 1 ) / i ;        printf("%I64dn", a[n] );    }    return 0;}