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, n;
  cin >> t;
  while (t--) {
    cin >> n;
    int a[n], m = 0, idx = 0;
    for (int i = 0; i < n; i++) cin >> a[i];
    bool check = true;
    for (int i = 1; i < n; i++)
      if (a[i] != a[i - 1]) check = false;
    for (int i = 1; i < n - 1; i++) {
      if ((a[i] > a[i - 1] || a[i] > a[i + 1]) && a[i] > m) {
        m = a[i];
        idx = i;
      }
    }
    if (a[0] > a[1] && a[0] > m) {
      m = a[0];
      idx = 0;
    }
    if (a[n - 1] > a[n - 2] && a[n - 1] > m) {
      m = a[n - 1];
      idx = n - 1;
    }
    if (check)
      cout << -1 << "\n";
    else
      cout << idx + 1 << "\n";
  }
  return 0;
}
