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() {
  int t;
  cin >> t;
  while (t--) {
    int n, max, notSame = 1;
    cin >> n;
    vector<int> arr(n, 0);
    for (int i = 0; i < n; i++) {
      cin >> arr[i];
    }
    for (int i = 1; i < n; i++) {
      if (arr[i] != arr[0]) {
        notSame = 0;
        break;
      }
    }
    if (notSame == 1) {
      cout << -1 << "\n";
    } else {
      max = *max_element(arr.begin(), arr.end());
      for (int i = 0; i < n; i++) {
        if (max == arr[i] && arr[i - 1] < arr[i]) {
          cout << i + 1 << "\n";
          break;
        }
        if (max == arr[i] && arr[i + 1] < arr[i]) {
          cout << i + 1 << "\n";
          break;
        }
      }
    }
  }
  return 0;
}
