#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 9;
const int mod = 1e9 + 7;
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t;
cin >> t;
while(t--){
int n;
cin >> n;
int arr[n];
for(int i = 0; i < n; i++) cin >> arr[i];
sort(arr, arr + n);
int cnt = 0;
for(int i = n - 1; i >= 0; i--){
if(arr[i] == arr[n - 1]) cnt++;
}
if(cnt > 2) cout << -1 << "\n";
else if(cnt == 2) cout << n - 1 << "\n";
else cout << n << "\n";
}
return 0;
}