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;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    long long int mx = 0, token;
    bool flag = true;
    int ans = 0;
    int label = 0;
    for (int i = 0; i < n; i++) {
      cin >> token;
      if (label == 0)
        label = token;
      else if (token != label)
        flag = false;
      if (token > mx) ans = i + 1;
    }
    if (flag == true)
      cout << -1 << endl;
    else
      cout << ans << endl;
  }
  return 0;
}
