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;
void solve() {
  int n;
  cin >> n;
  int a[n];
  vector<int> v;
  for (int i = 0; i < n; i++) cin >> a[i];
  int t = *max_element(a, a + n);
  for (int i = 0; i < n; i++) {
    if (a[i] == t) {
      if (a[i] > a[i - 1] || a[i] > a[i + 1]) {
        cout << (i + 1) << endl;
        return;
      }
    }
  }
  cout << -1 << endl;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  ;
  int test;
  cin >> test;
  while (test--) {
    solve();
  }
}
