#include <bits/stdc++.h>
#define int long long
using namespace std;
 
void solve() {
    int n;
    cin >> n;
    vector<int> v(n);
    int maxi=INT_MIN;
    for(int i=0;i<n;i++){
    	cin>>v[i];
		maxi=max(maxi,v[i]);
    }
    for(int i=0;i<n;i++){
    	if(v[i]==maxi){
    		if(i-1>=0 && v[i-1]<maxi){
    			cout<<i+1<<endl;
    			return;
    		}
    		if(i+1<n && v[i+1]<maxi){
    			cout<<i+1<<endl;
    			return;
    		}
    	}
    }
    cout<<-1<<endl;
 
 
 
}
 
signed main() {
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}
 

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6
5
5 3 4 4 5
3
1 1 1
5
4 4 3 4 4
5
5 5 4 3 2
3
1 1 2
5
5 4 3 5 5