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

t = int(input())
for _ in range(t):
    _ = int(input())
    fish_tank = list(map(int, input().split()))
    max_val = max(fish_tank)
    result = -1
    for i in range(len(fish_tank)):
        if fish_tank[i] == max_val:
            if i > 0 and fish_tank[i - 1] != max_val:
                result = i + 1
            if i < len(fish_tank) - 1 and fish_tank[i + 1] != max_val:
                result = i + 1
    print(result)
