#include <bits/stdc++.h>
using namespace std;
int main(void) {
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);
  int 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;
  }
  return 0;
}
