Hint 3 prod just takes the product of all the elements in list n . What happens when you add the product of all of the moduli besides one ? <| sep |> I can somewhat relate . After living in Asia for 4 years and then coming back to the west , it ' s been very difficult for me to hug people and even shake hands after not doing it at all . I never noticed it before but something about it seems very fake to me . Like , why do I have to hug everyone in the room if I am leaving and say goodbye one at a time . Why can ' t I just do a wave and say goodbye to everyone at once . People will get offended if I ' m not overly huggy . Most of the times , if I ' m at a large party , I will just try to sneak out the back to avoid the awkwardness of having to give everyone a hug . I ' ve gotten better with giving handshakes but I always wonder when was the last time that fucker jacked off with that same hand and then I freak out .