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 inf = 1e9 + 7;
int main() {
  ios::sync_with_stdio(false);
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    long long *a = new long long[n + 1];
    long long maxn = 0;
    int num = 0;
    for (int i = 1; i <= n; i++) {
      cin >> a[i];
      if (maxn < a[i]) {
        maxn = a[i];
        num = 1;
      } else if (maxn == a[i]) {
        num++;
      }
    }
    if (num == n)
      cout << -1 << endl;
    else {
      int index = 0;
      for (int i = 1; i <= n; i++) {
        if (maxn == a[i]) {
          if (i == 1) {
            if (a[i] > a[i + 1]) {
              index = i;
              break;
            }
          } else if (i == n) {
            if (a[i] > a[i - 1]) {
              index = i;
              break;
            }
          } else {
            if (a[i] > a[i + 1] || a[i] > a[i - 1]) {
              index = i;
              break;
            }
          }
        }
      }
      cout << index << endl;
    }
  }
  return 0;
}
