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 long long MOD = 1e+9 + 7;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cout << fixed;
  cout << setprecision(10);
  ;
  long long t;
  cin >> t;
  while (t--) {
    long long n;
    cin >> n;
    long long a[n];
    for (long long i = 0; i < n; i++) cin >> a[i];
    long long mx = -1;
    for (long long i = 0; i < n; i++) {
      if (a[i] > mx) {
        mx = a[i];
      }
    }
    long long f = 0, ind = 0;
    for (long long i = 0; i < n; i++) {
      if (a[i] == mx) {
        if ((i - 1 >= 0 && a[i - 1] < a[i]) || (i + 1 < n && a[i] > a[i + 1])) {
          ind = i + 1;
          f = 1;
          break;
        }
      }
    }
    if (f) {
      cout << ind << endl;
    } else {
      cout << "-1\n";
    }
  }
}
