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() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  long long tc = 1;
  cin >> tc;
  while (tc--) {
    long long n;
    cin >> n;
    long long arr[n];
    set<long long> st;
    for (long long i = 0; i < n; i++) {
      cin >> arr[i];
      st.insert(arr[i]);
    }
    if (st.size() == 1) {
      cout << "-1\n";
      continue;
    }
    auto idx = max_element(arr, arr + n) - arr;
    long long ans = idx;
    for (long long i = idx; i < n - 1; i++) {
      if (arr[i] != arr[i + 1]) {
        ans = i;
        break;
      }
    }
    cout << ans + 1 << "\n";
  }
}
