#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  int n;
  for (int i = 0; i < t; i++) {
    cin >> n;
    if (n <= 2) {
      cout << 0 << endl;
      continue;
    }
    if (n % 2 == 0)
      cout << (n / 2) - 1 << endl;
    else
      cout << n / 2 << endl;
  }
  return 0;
}
