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

for efkjr in range(int(input())):
    a = int(input())
    our = list(map(int, input().split()))
    dom_weight = max(our)
    found = False
    for i in range(a):
        if our[i] == dom_weight:
            if i > 0 and our[i - 1] < our[i]:
                print(i + 1)
                found = True
                break
            if i < a - 1 and our[i] > our[i + 1]:
                print(i + 1)
                found = True
                break
    if not found:
        print(-1)
