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()))
    maximum = max(arr)
    ans = -1
    for i in range(n):
        if(arr[i]==maximum):
            if((i>=1 and arr[i]>arr[i-1]) or (i<n-1 and arr[i]>arr[i+1])):
                ans = i+1
                break
    print(ans)