#include <iostream> using namespace std; int a(int n) { int sum = 1; for (int i = n; i > 0; i--) { sum *= i; } return sum; } int main() { int n; cin >> n; int sum = 0; int now; for (int i = 1; i <= n; i++) { now = a(i); if (i % 2 == 1) { sum += now; } else if (i % 2 == 0) { sum -= now; } } cout << sum; return 0; }