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;
  scanf("%d", &t);
  while (t--) {
    int n;
    cin >> n;
    int *a, *b;
    a = (int *)malloc(sizeof(int) * (n + 5));
    b = (int *)malloc(sizeof(int) * (n + 5));
    for (int i = 1; i <= n; i++) {
      cin >> a[i];
      b[i] = a[i];
    }
    int pos = 0;
    sort(b + 1, b + n + 1);
    for (int i = 1; i <= n; i++) {
      if (b[n] == a[i] && (a[i] > a[i + 1])) {
        pos = i;
        break;
      }
    }
    if (b[n] == b[1]) {
      cout << -1 << endl;
    } else
      cout << pos << endl;
  }
  return 0;
}
