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

test_case = int(input())
for _ in range(test_case):
    n = int(input())
    a = list(map(int, input().split()))
    if len(set(a)) == 1:
        print(-1)
    else:
        max_idx = -1
        max_ele = max(a)
        for i in range(n):
            if a[i] == max_ele:
                max_idx = i + 1
                break
        print(max_idx)