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