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 i in range(int(input())):
    n = int(input())
    l = list(map(int,input().split()))
    s = l.copy()
    a = set(l)
    if len(a)==1:
        print(-1)
    else:
        s.sort(reverse=True)
        for i in range(n):
            if l[i]==s[0]:
                print(i+1)
                break
            