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() {
  long long int times;
  cin >> times;
  while (times--) {
    long long int n;
    cin >> n;
    long long int arr[n];
    long long int max = 0;
    for (long long int i = 0; i < n; i++) {
      cin >> arr[i];
      if (max < arr[i]) {
        max = arr[i];
      }
    }
    long long int num = arr[0];
    long long int tag = 0;
    for (long long int i = 0; i < n; i++) {
      if (arr[i] != arr[0]) {
        tag = 1;
        break;
      }
    }
    if (tag == 0) {
      cout << -1 << endl;
    } else {
      long long int ans = -1;
      for (long long int i = 0; i < n; i++) {
        if (arr[i] == max) {
          if (i == 0 && (arr[i + 1] < arr[i])) {
            ans = i + 1;
            break;
          } else if (i == (n - 1) && (arr[i - 1] < arr[i])) {
            ans = i + 1;
            break;
          } else {
            if ((arr[i + 1] < arr[i]) || (arr[i - 1] < arr[i])) {
              ans = i + 1;
              break;
            }
          }
        }
      }
      cout << ans << endl;
    }
  }
}
