str = input('请输入你要加密的字符串:')
num = int(input('请输入你的密钥:'))
if num>26:
num = num % 26
for i in str:
if ord(i)>122-num:
jia = ord(i)-26+num
else:
jia = ord(i)+num
print(chr(jia),end='')
str = input('请输入你要解密的字符串:')
num = int(input('请输入解密密钥:'))
if num>26:
num = num %26
for i in str:
if ord(i)<97+num:
jie = ord(i)+26-num
else:
jie = ord(i)-num
print(chr(jie),end='')