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;
int32_t main() {
  long long t;
  cin >> t;
  while (t--) {
    long long n;
    cin >> n;
    long long a[n];
    long long mx = -1, id = -1;
    for (long long i = 0; i < n; i++) {
      cin >> a[i];
      if (a[i] > mx) {
        mx = a[i];
      }
    }
    long long flag = 0;
    for (long long i = 0; i < n; i++) {
      if (a[i] != mx) {
        flag = 1;
        break;
      }
    }
    if (flag == 0) {
      cout << -1 << endl;
    } else {
      for (long long i = 1; i < n; i++) {
        if (a[i] == mx && a[i] > a[i - 1]) {
          id = i;
        }
      }
      if (id == -1) {
        for (long long i = 0; i < (n - 1); i++) {
          if (a[i] == mx && a[i + 1] < a[i]) {
            id = i;
          }
        }
      }
      cout << (id + 1) << endl;
    }
  }
  return 0;
}
