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

from sys import stdin

t = int(stdin.readline().strip())

for _ in range(t):
    n = int(stdin.readline().strip())
    arr = [int(x) for x in stdin.readline().strip().split(" ")]

    grt = max(arr)
    found = False

    for idx, val in enumerate(arr):
        if val == grt:
            if idx - 1 >= 0 and arr[idx - 1] < grt or idx + 1 <= len(arr) - 1 and arr[idx + 1] < grt:
                print(idx + 1)
                found = True
                break
    
    if not found:
        print(-1)
    