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 _ in range(t):
    n=int(input())
    l= list(map(int,input().split()))
    x=max(l)
    y=-1
    for i in range(1,n-1):
        if l[i]==x and (l[i+1]!=x or l[i-1]!=x):
            y=i+1
            break
    if l[0]==x and l[1]!=x:
        y=1
    if l[-1]==x and l[-2]!=x:
        y=n
    print(y)