Paths on a Grid

http://poj.org/problem?id=1942

#include<map>#include<set>#include<list>#include<cmath>#include<ctime>#include<deque>#include<stack>#include<bitset>#include<cstdio>#include<vector>#include<cstdlib>#include<cstring>#include<iomanip>#include<numeric>#include<sstream>#include<utility>#include<iostream>#include<algorithm>#include<functional>using namespace std ;unsigned long long n , m , temp , sum = 0 , ans = 0 , i; int main(){while( scanf( "%llu%llu" , &n , &m ) != EOF ){if( !n && !m )break ;ans = 1 ;if( n > m )swap( n , m ) ;sum = n + m ;for( i = 1 ; i <= n ; ++i ){ans = ans * ( sum - i + 1 ) / i ;}printf( "%llu\n" , ans ) ;}     return 0;}