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 _ in range(int(input())):
    n=int(input())
    c=-1
    m=-1
    a=[int(x) for x in input().split()]
    if(a[0]>a[1]):
        c=1
        m=a[0]
    for i in range(1,n-1):
        if(a[i]>a[i-1] or a[i]>a[i+1]):
            if(a[i]>m):
                c=i+1
                m=a[i]
    if(a[n-1]>a[n-2]):
        if(a[n-1]>m):
            c=n-1+1
    
    print(c)
    
        
        
            