https://school.programmers.co.kr/learn/courses/30/lessons/148653
def solution(storey):
answer = 0
n = storey
while n :
r = n % 10
if r > 5 :
answer += (10-r)
n += 10
elif r < 5 :
answer += r
else : # 5
if (n//10) % 10 > 4:
n += 10
answer += r
n = n//10
return answer