#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int t;
  cin >> t;
  while (t--) {
    long long int n;
    cin >> n;
    if (n <= 2) {
      cout << 0 << '\n';
    } else {
      if (n % 2 == 0)
        cout << (n / 2) - 1 << '\n';
      else
        cout << (n / 2) << '\n';
    }
  }
}
