#include <bits/stdc++.h>
using namespace std;
int main() {
  unsigned long long n;
  scanf("%lld", &n);
  unsigned long long ans = 1;
  for (unsigned long long i = 1; i <= n; i++) {
    ans *= i;
  }
  ans /= ((n / 2) * (n / 2));
  printf("%lld", ans / 2);
}
