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 a0 in range(int(input())):
    n=int(input())
    l=[int(x) for x in input().split()]
    m=max(l)
    for i in range(n):
        if i>0:
            if l[i]==m and l[i-1]<l[i]:
                print(i+1)
                break
        if i<n-1:
            if l[i]==m and l[i+1]<l[i]:
                print(i+1)
                break
    else:
        print(-1)