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

def apt(n, arr):
    
    temp = max(arr)
    index = -1
    for i in range(n):
        
        if i == 0 and arr[i] == temp and arr[i + 1] != temp:
            index = i + 1
        elif i == n - 1 and arr[i] == temp and arr[i - 1] != temp:
            index = i + 1
            
        elif (i != 0 and i != n - 1) and arr[i] == temp and (arr[i - 1] != temp or arr[i + 1] != temp):
            index = i + 1
            
    return index
        

        
 
 
t = int(input())
for i in range(t):
    
    n = int(input())
    arr = list(map(int, input().split()))
    print(apt(n, arr))