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() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int T;
  cin >> T;
  while (T--) {
    int n, c = -1, k = 1, i;
    cin >> n;
    long long a[n];
    for (i = 0; i < n; i++) {
      cin >> a[i];
      if (c < a[i]) c = a[i];
    }
    if (a[0] == c && a[1] < a[0]) {
      cout << 1 << "\n";
      continue;
    }
    if (a[n - 1] == c && a[n - 2] < a[n - 1]) {
      cout << n - 1 << "\n";
      continue;
    }
    for (i = 1; i < n - 2; i++) {
      if (a[i] == c && (a[i - 1] < a[i] || a[i + 1] < a[i])) {
        cout << i + 1 << "\n";
        k = -1;
        break;
      }
    }
    if (k != -1) cout << -1 << "\n";
  }
  return 0;
}
