GPT答：

7i24.cn

s = input("请输入获得的密文：")
plaintext = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
ciphertext = "DEFGHIJKLMNOPQRSTUVWXYZABC"

result = ""
for char in s:
    if char.isalpha():
        if char.islower():
            index = plaintext.index(char.upper())
            result += ciphertext[index].lower()
        else:
            index = plaintext.index(char)
            result += ciphertext[index]
    else:
        result += char

print("解密后的明文为：" + result)