凯撒密码

plaincode = input("")
for p in plaincode:
if ord("a") <= ord(p) <= ord("z"):
print(chr(ord("a")+(ord(p)-ord("a")+3)%26),end='')
elif ord("A") <= ord(p) <= ord("Z"):
print(chr(ord("A")+(ord(p)-ord("A")+3)%26),end='')
else:
print(p,end='')