def encryption(plaintext, keyword):
    txt_len = len(plaintext)
    keyword *= txt_len // len(keyword) + 1
    keyword = keyword[:txt_len]
    encoded = ""
    for c in range(txt_len):
        newchar = ord(plaintext[c]) + ord(keyword[c]) - 194
        newchar %= 25
        encoded += chr(newchar + 97)
    return encoded