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;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    vector<int> arr(n);
    int maximum = 0;
    for (int i = 0; i < n; i++) {
      cin >> arr[i];
      maximum = max(maximum, arr[i]);
    }
    int ans = -1;
    for (int i = 0; i < n; i++) {
      if (arr[i] == maximum) {
        if (i == 0) {
          if (arr[1] != arr[0]) {
            ans = 1;
            break;
          }
        } else if (i == n - 1) {
          if (arr[n - 2] != arr[n - 1]) {
            ans = i + 1;
            break;
          }
        } else {
          if (arr[i] != arr[i - 1] || arr[i] != arr[i + 1]) {
            ans = i + 1;
            break;
          }
        }
      }
    }
    cout << ans << endl;
  }
  return 0;
}
