Visitor with most amount of time

<https://app.dataquest.io/m/353/working-with-dates-and-times-in-python/11/next-steps

Screen Link: < https://app.dataquest.io/m/353/working-with-dates-and-times-in-python/11/next-steps

#vistor who spent the most time at the white house
lenght=potus[1][3]-potus[1][2]
vistors_name='None'
for row in potus:
    start_apt=row[2]
    end_apt=row[3]
    meeting_lenght=end_apt-start_apt
    if meeting_lenght>lenght:
        lenght=meeting_lenght
        vistors_name=row[0]
#print("The vistor who spent the most time,that's {0} is {1}".format(lenght,vistors_name))

Just want to confirm if my code is right. Plus to receive suggestions on other approaches to solve this question.

Are there any improvements required for my code or redundancies in my code