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;
const int N = 1e6 + 10;
int n, a[N];
int main() {
  ios::sync_with_stdio(0);
  int t;
  cin >> t;
  while (t--) {
    cin >> n;
    int flag = 0, index = 1;
    for (int i = 1; i <= n; i++) {
      cin >> a[i];
      if (i != 1 && a[i] != a[i - 1]) flag = 1;
      if (a[index] < a[i]) index = i;
    }
    if (!flag)
      cout << -1 << endl;
    else
      cout << index << endl;
  }
  return 0;
}
