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())
    list1=list(map(int,input().strip().split()))
    
    index=-1
    temp=max(list1)
    for i in range(n):
        if list1[i]==temp:
            if (i-1)>=0 and list1[i-1]<temp or (i+1)<n and list1[i+1]<temp:
                index=i+1
                break
    
    print(index)
            
    
    
    
    
    
    
