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() {
  long long t;
  cin >> t;
  while (t--) {
    long long n;
    cin >> n;
    vector<long long> v(n);
    for (long long i = 0; i < n; i++) {
      cin >> v[i];
    }
    map<long long, long long> m;
    for (long long i = 0; i < n; i++) {
      m[v[i]]++;
    }
    if (m.size() == 1) {
      cout << -1 << endl;
    } else {
      long long m = *max_element(v.begin(), v.end());
      for (long long i = 0; i < n; i++) {
        if (v[i] == m) {
          if (i == 0 && v[i + 1] != m) {
            cout << i + 1 << endl;
            break;
          } else if (i == n - 1 && v[i - 1] != m) {
            cout << i + 1 << endl;
            break;
          } else {
            if (v[i + 1] != m || v[i - 1] != m) {
              cout << i + 1 << endl;
              break;
            }
          }
        }
      }
    }
  }
  return 0;
}
