B - Factorial

#include <bits/stdc++.h>
using namespace std;

#define int long long

int n;
int f[25];

signed main()
{
    cin >> n;
    f[0] = 1;
    for(int i = 1; i <= n; i++){
        f[i] = f[i - 1] * i;
    }
    cout << f[n] << endl;
}