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 i in range(t):
    n=int(input())
    l=list(map(int,input().split()))
    a=max(l)
    b=min(l)
    if a==b:
        print('-1')
    else:
        for j in range(n):
            if l[j]==a:
                if j>0 and l[j-1]<a:
                    print(j+1)
                    break
                elif j<n-1 and l[j+1]<a:
                    print(j+1)
                    break