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;
    cin >> n;
    int flag = 1;
    int mx = INT_MIN;
    int index = 0;
    vector<int> vec(n);
    for (int i = 0; i < n; i++) {
      int temp;
      cin >> temp;
      vec[i] = temp;
      if (temp > mx) {
        mx = temp;
      }
    }
    for (int i = 0; i < n - 1; i++) {
      if (vec[i] < mx) {
        index = i;
        break;
      }
    }
    for (int i = 0; i < n - 1; i++) {
      if (vec[i] != vec[i + 1]) {
        flag = 0;
        break;
      }
    }
    if (flag) {
      cout << -1 << endl;
      continue;
    }
    cout << index + 1 << endl;
  }
}
