各位大佬，这个问题怎样用python语言解决哇？

# -*- coding: UTF-8 -*-
x = int(input("多少个西瓜？"))

days = 0
while (x > 0):
    x = x / 2 - 2
    if x < 0:
        x = 0
    days = days + 1
    print("...第" + str(days) + "天后还有" + str(x) + "个")
print("需要" + str(days) + "天")

def fun(n):
    day=0;
    while(n>0):
        n=n-n/2-2
        day=day+1
    print(day)

n=input()
fun(int(n))