这题只能用C++写,害得我复习了一下C++语法@烤点老白薯

#include <iostream>
using namespace std;

long long factorial(int n);

int main() {

    int n;
    cin >> n;

    cout << factorial(n) << endl;

    return 0;
}

long long factorial(int n) {

    long long x = 1;
    for (int i=1;i<=n;i++){
        x *= i;
    }
    
    return x;
}