I checked several times and everything is working correctly, help me


def encryption(txt):
    cipher = {'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4, 'f': 5, 'g': 6, 'h': 7, 'i': 8, 'j': 9, 'k': 10, 'l': 11, 'm': 12, 'n': 13, 'o': 14, 'p': 15, 'q': 16, 'r': 17, 's': 18, 't': 19, 'u': 20, 'v': 21, 'w': 22, 'x': 23, 'y': 24, 'z': 25}


    encryption_list = []
    for i in txt:
        encryption_list.append(cipher[i])

    c = d = c1 = 0
    encryption_last_list = []
    for i in encryption_list:
        if d == 0:
            d += 1
            c = i
            i -= 5

            if i < 0:
                i = 25 - abs(i)
            encryption_last_list.append(i)

        else:
            c1 = i
            i -= c
            c = c1
            if i < 0:
                i = 26 - abs(i)
            encryption_last_list.append(i)

    decodding_list = []
    for i in encryption_last_list:
        for k, v in cipher.items():
            if v == i:
                decodding_list.append(k)

    return decodding_list

text = input()
if len(text) <= 99:
    c = ''
    output = encryption(text.lower())
    for i in output:
        c += i
    print(c)