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()))
    b=list(a)
    m=max(a)
    i=a.index(m)
    if a.count(m)==len(a):
        print(-1)
    else:
        if i==0:
            while a[i]==a[i+1]:
                i+=1
        print(i+1)