#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  long long t;
  cin >> t;
  while (t--) {
    long long n;
    cin >> n;
    if (n <= 2) {
      cout << "0" << endl;
    } else {
      if (n & 1) {
        cout << n / 2 << endl;
      } else {
        cout << ((n / 2) - 1) << endl;
      }
    }
  }
}
