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

def calc(n,a):
    maxele=max(a)
    if a.count(maxele)==n:
        return -1
    for i in range(n):
        if i==0 or i==n-1:
            if i==0 and a[i]==maxele and a[i]>a[i+1] or i==n-1 and a[i]==maxele and a[i]>a[i-1]:
                return i+1
        else:
            if a[i]==maxele and (a[i]>a[i-1] or a[i]>a[i+1]):
                return i+1
    return -1
t=int(input())
for i in range(t):
    n=int(input())
    a=list(map(int,input().split()))
    print(calc(n,a))