1
3
5 3 4
 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
 1
3
10 1 5

1
 1
-1
2
2
3
1
 1

#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  int t, n, ans, sig;
  cin >> t;
  while (t--) {
    cin >> n;
    int arr[n];
    ans = 0;
    sig = 0;
    for (int i = 0; i < n; i++) cin >> arr[i];
    for (int i = 1; i < n; i++) {
      if (arr[i] != arr[0]) {
        sig = 1;
        break;
      }
    }
    if (sig == 1) {
      for (int i = 1; i < n; i++) {
        if (arr[i] > arr[ans]) ans = i;
      }
      cout << ans << endl;
    } else
      cout << -1 << endl;
  }
}
