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

# cook your dish here
for _ in range(int(input())):
    n=int(input())
    a=[int(x) for x in input().split()]
    m=max(a)
    x=a.index(m)
    if x:
        print(x+1)
    else:
        for i in range(1,n):
            if a[i]!=m:
                print(x+1)
                break
            x=i
        else:
            print(-1)
    