#1
key = 7
message = "Hello"
def encrypt(message, key):
    message = message.lower()
    secret = ""
    for c in message:
        if c in "abcdefghijklmnopqrstuvwxyz":
            num = ord(c)
            num += key
            if num > ord("z"):
                 num -= 26
            elif num < ord("a"):
                num += 26
            secret = secret + chr(num)
        else:
# don't modify any non-letters in the message; just add them as-is
            secret = secret + c
    return secret


#2

key = -7
message = "Hello"
def decrypt(message, key):
        message = message.lower()
        secret = ""
        for c in message:
                if c in "abcdefghijklmnopqrstuvwxyz":
                        num = ord(c)
                        num += key
                        if num > ord("z"):
                                num -= 26
                        elif num < ord("a"):
                                num += 26
                        secret = secret + chr(num)
                else:
                        # don't modify any non-letters in the message; just add them as-is
                        secret = secret + c
        return secret

cypher = decrypt("Hello", -7)
plaint = encrypt(cypher, 7)

print cypher
print plaint