我的“凯撒密码”
str=input()
a='abcdefghijklmnopqrstuvwxyz'
b='ABCDEFGHIJKLMNOPQRSTUVWXYZ'
for i in range(len(str)):
if str[i] == " ":
print(" ", end="")
elif str[i] in a:
for j in range(len(a)):
if str[i]==a[j]:
print(a[(j+3)%26],end="")
elif str[i] in b:
for k in range(len(b)):
if str[i]==b[k]:
print(b[(k+3)%26],end="")
else:
print(str[i],end="")