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 __ in range(int(input())):
    n = int(input())
    a = list(map(int, input().split()))
    ma = max(a)
    answer = -1
    for i in range(n):
        if a[i] == ma:
            if i-1 >= 0 and a[i-1] < ma:
                answer = i+1
                break
            if i+1 < n and a[i+1] < ma:
                answer = i+1
                break
    print(answer)
