#include <bits/stdc++.h>
using namespace std;
#define IOS ios_base::sync_with_stdio(false),cin.tie(NULL),cout.tie(NULL);
#define ll long long

int main() {
    IOS

    int t;cin>>t;
    while(t--){
        int n;cin>>n;
        vector<int>v(n);
        for(int i = 0;i<n;i++)
            cin>>v[i];
        sort(v.rbegin(),v.rend());
        int ans=-1;
        int i=0;
        while(i+1<n&&v[i]==v[i+1])
            i++;
        if(i==1)
            ans=n-1;
        else if(i>=2)
            ans=-1;
        else ans=n;
        cout<<ans<<"\n";

    }


};