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(0, t):
    n= int(input())
    lst= list(map(int, input().split()))
    high= max(lst)
    ans=-1
    
    for j in range(0, n):
        if(lst[j]==high):
            if(j==0 and lst[j]>lst[j+1]):
                ans=j+1
                break
            
            elif(j==n-1 and lst[j]>lst[j-1]):
                ans=j+1
                break
            
            elif(j!=0 and j!=n-1):
                if(lst[j]>lst[j+1] or lst[j]>lst[j-1]):
                    ans=j+1
                    break
            
    print(ans)