#include <iostream>
#include "algorithm"
#include "cmath"
using namespace std;
int main() {

    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int tt;
    cin >> tt;
    while (tt--) {
        int size;
        cin >> size;
        long long arr[size];
        for (int i = 0; i < size; i++) {
            cin >> arr[i];
        }
        int counter = 0;
        for (int j = 0; j < size; j++) {
            int max = arr[j];
            for (int k = j + 1; k < size; k++) {
                if (max == arr[k]) {
                    counter++;

                }

            }


        }
        if (counter == 1) {
            cout << size - 1 << endl;
        }
        else if (counter == 0) {
            cout << size << endl;
        }
        else
            cout << -1 << endl;
       
            
    }
}