5.1.11

#include <iostream>
#include <cmath>

using namespace std;
int main()
{
    int n, s, d;
    cin >> n;
    s = 0;
    d = 1;
    for (int i = 1; i <= n; i++) {
        d *= i;
        s += pow(-1, (i + 1)) * d;
    }
    cout << s;
}