L1-084 拯救外星人 分數 10

// 1'21"
#include <iostream>
using namespace std;
#define int long long
signed main()
{
    int n, m;
    cin >> n >> m;
    int s = n + m;
    int sum = 1;
    for(int i = 1; i <= s; ++ i)
        sum *= i;
    cout << sum;
    return 0;
}