Untitled

#include <iostream>
using namespace std;
int main() {
	int a, b, c;
	cin >> c;
	for (int i = 0; i < c; i++){
		cin >> a;
		if (a <= 2) cout << 0 << endl;
		else if (a % 2 == 0) cout << a / 2 - 1 << endl;
		else cout << a / 2 << endl;
	}
}