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 i in range(t):
    n = int(input())
    s = list(map(int, input().split()))
    x = max(s)
    if s[0] != x:
        print(s.index(x) + 1)
    else:
        for j in range(n):
            if s[j] != x:
                print(j)
                break
        else:
            print(-1)
