#include <bits/stdc++.h>
using namespace std;
int main() {
  unsigned long long int n;
  cin >> n;
  unsigned long long int f = 1;
  for (unsigned long long int i = n - 1; i >= 1; i--) f = f * i;
  n = n / 2;
  f = f / n;
  cout << f << "\n";
  return 0;
}
