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

tests = int(input())
answers = []
for test in range(tests):
    n = int(input())
    x = list(map(int, input().split()))
    f = max(x)
    for i in range(len(x)):
        if i < n-1:
            if x[i] == f and x[i+1] != f:
                answers.append(i+1)
                break
        if i > 0:
            if x[i] == f and x[i-1] != f:
                answers.append(i+1)
                break
    else:
        answers.append(-1)

for i in answers:
    print(i)
