#include <iostream>
using namespace std;

int main() {
  long long N;
  cin >> N;

  double n = N;
  for (long long i = 1; i <= N / 2; i++) {
    if ((long long)(n / i + 0.5) % 2 == 0) {
      cout << (N / 2 - i + 1) * 2 - (N % 2 == 0 ? 1 : 0) << endl;
      return 0;
    }
  }

  cout << 0 << endl;

  return 0;
}