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>
#pragma GCC optimize("Ofast")
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    vector<int> a(n);
    set<int> check;
    for (int i = 0; i < n; i++) {
      cin >> a[i];
      check.insert(a[i]);
    }
    if (check.size() == 1) {
      cout << -1 << '\n';
      continue;
    }
    int idxMx = 0, mx = 0;
    for (int i = 0; i < n; i++) {
      if (i == 0) {
        mx = a[i];
        idxMx = i;
        continue;
      }
      if (i == n - 1) {
        if (mx < a[i] && a[i] > a[i - 1]) {
          mx = a[i];
          idxMx = i;
          break;
        }
      }
      if (mx <= a[i]) {
        if (a[i - 1] < a[i] || a[i + 1] < a[i]) {
          mx = a[i];
          idxMx = i;
        }
      }
    }
    cout << idxMx + 1 << '\n';
  }
  return 0;
}
