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 a[300005];
int main() {
  int t, n;
  scanf(" %d", &t);
  while (t--) {
    scanf(" %d", &n);
    for (int i = 0; i < n; i++) {
      scanf(" %d", &a[i]);
    }
    bool found = true;
    for (int i = 1; i < n; i++) {
      if (a[i] != a[0]) {
        found = false;
        break;
      }
    }
    if (found) {
      printf("-1\n");
      continue;
    }
    int maxi = 0;
    for (int i = 1; i < n; i++) {
      if (a[maxi] < a[i]) {
        maxi = i;
      } else if (a[maxi] == a[i]) {
        if (i + 1 < n && a[i] > a[i + 1])
          maxi = i;
        else if (a[i] > a[i - 1])
          maxi = i;
      }
    }
    printf("%d\n", maxi + 1);
  }
}
