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())
    arr = list(map(int,input().split()))

    max = 0
    val = 0
    i = 0
    

    while i < n:
        if i - 1 < 0:
            if arr[i+1] < arr[i]:
                
                if arr[i] > val:
                    val = arr[i]
                    max = i + 1
                
        elif i + 1 > n-1:
            if arr[i-1] < arr[i]:

                if arr[i] > val:
                    val = arr[i]
                    max = i + 1

        elif arr[i+1] < arr[i] or arr[i-1] < arr[i]:

            if arr[i] > val:
                val = arr[i]
                max = i + 1

        i += 1

    if max == 0:
        print(-1)
    else:
        print(max)
                    
