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;
    vector<int> a(n);
    for (int i = 0; i < n; i++) {
      cin >> a[i];
    }
    if (set<int>(a.begin(), a.end()).size() == 1) {
      puts("-1");
    } else {
      int mx = *max_element(a.begin(), a.end());
      for (int i = 0; i < n; i++) {
        if (i > 0 and a[i] == mx and a[i - 1] != mx) {
          printf("%d\n", i + 1);
          break;
        } else if (i < n - 1 and a[i] == mx and a[i + 1] != mx) {
          printf("%d\n", i + 1);
          break;
        }
      }
    }
  }
  return 0;
}
