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 maxn = 3e5 + 10;
int a[maxn];
char s[10];
int main() {
  int t;
  scanf("%d", &t);
  while (t--) {
    int n;
    scanf("%d", &n);
    int ma = 0;
    for (int i = 1; i <= n; i++) {
      scanf("%d", &a[i]);
      ma = max(ma, a[i]);
    }
    int fla = 0;
    for (int i = 1; i <= n; i++) {
      if (a[i] == ma) {
        if ((a[i - 1] < a[i] && i - 1 >= 1) ||
            (a[i + 1] < a[i] && i + 1 <= n)) {
          fla = i;
          break;
        }
      }
    }
    if (fla == 0)
      cout << "-1" << endl;
    else
      cout << fla << endl;
  }
  return 0;
}
