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 proC(arr):
    k=max(arr)
    for i in range(len(arr)):
        if(arr[i]==k):
            if(0<=i-1 and arr[i]>arr[i-1]):
                return i+1
            if(i+1<=len(arr)-1 and arr[i]>arr[i+1]):
                return i+1
    return -1
t=int(input())
for i in range(t):
    n=int(input())
    arr=list(map(int,input().split()))
    print(proC(arr))