https://school.programmers.co.kr/learn/courses/30/lessons/12948
def solution(phone_number):
answer = ''
s = list(phone_number)
size=len(s)
for i in range(size-4):
answer+="*"
for i in range(size-4,size):
answer +=s[i]
return answer
def hide_numbers(s):
return "*"*(len(s)-4) + s[-4:]