#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 100;
long long a[N];
int main() {
  int t;
  cin >> t;
  while (t--) {
    long long n;
    cin >> n;
    if (n == 1 || n == 2)
      puts("0");
    else {
      if (n % 2 == 0)
        cout << n / 2 - 1 << endl;
      else
        cout << n / 2 << endl;
    }
  }
  return 0;
}
