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())
    a=list(map(int,input().split()))
    if len(set(a))==1:
        print(-1)
    else:
        m=max(a)
        for i in range(n):
            if a[i]==m and ((i-1>=0 and a[i-1]<a[i]) or (i+1<n and a[i+1]<a[i])):
                print(i+1)
                break
               
                
