Code (C++):

#include<bits/stdc++.h>
using namespace std;
const long long M=3e5+10,MOD=1000000000;
typedef long long ll;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int t=1;
    cin>>t;
    while(t--){
     int n;
     cin>>n;
     int answer=n/2;
     if(n%2==0)answer--;
     cout<<answer<<"\n";
    }


   
   return 0;
 
}