def binary_to_ascii(binary_message):
    ascii_list = list()
    for byte in binary_message:
        byte = byte[::-1]
        acc = 0
        for i in range(len(byte)):
            acc += int(byte[i])*(2**i)
        ascii_list.append(acc)
    return ascii_list

def caesar(ascii_list, key):
    s = ""
    for e in ascii_list:
        key = int(key)
        val = (e - key)

        if val < 0:
            val = 100 + ((e - key) % 26)
            if val > ord("z"):
                val -= 26

        s = s + chr(val)
    return s

def vig(ascii_list, key):
    s = ""
    for i in range(len(ascii_list)):
        index = i % len(key)
        e = ascii_list[i]
        #print(i, key[index])
        val = e - ord(key[index])
        s = s + chr(val)
    return s


def start(file_name):
    lines = open(file_name).read().splitlines()
    for line in lines:
        element_list = line.split(":")
        algorithm = element_list[0]
        key = element_list[1]
        message = element_list[2]
        letter_list = message.split(" ")
        ascii_list = binary_to_ascii(letter_list)
        if algorithm == "caesar":
            print(caesar(ascii_list, int(key)))
        else:
            print(vig(ascii_list, key))