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;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long T = 1;
  cin >> T;
  while (T--) {
    long long n;
    cin >> n;
    long long a[n], f = 0, m = 0;
    for (long long i = 0; i < n; i++) {
      cin >> a[i];
    }
    for (long long i = 0; i < n; i++) {
      if (i > 0 && i < n - 1) {
        if ((a[i] > m) && ((a[i] != a[i - 1]) || (a[i] != a[i + 1]))) {
          m = a[i];
          f = i + 1;
        }
      } else {
        if (i == 0 && a[i] > m && a[i] != a[i + 1]) {
          m = a[i];
          f = i + 1;
        }
        if (i == n - 1 && a[i] > m && a[i] != a[i - 1]) {
          m = a[i];
          f = i + 1;
        }
      }
    }
    if (f) {
      cout << f << "\n";
    } else {
      cout << -1 << "\n";
    }
  }
  return 0;
}
