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()))
    if min(s)==max(s):
        print(-1)
    else:
        m=s.index(max(s))
        if m==0:
            while s[m]==s[m+1]:
                m+=1
        print(m+1)