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