def generate_serial(name: str) -> str:
    if len(name) < 4:
        return "Need more characters!"
    if len(name) > 50:
        return "So many characters!"

    ebx = 0
    ecx = 0

    for i, ch in enumerate(name):
        ecx += 1
        ebx += ord(ch) ^ ecx

    eax = ord(name[-1]) ^ ecx
    eax *= 6
    ebx <<= 7
    eax += ebx

    return format(eax, 'X')


# Usage
if __name__ == '__main__':
    user_input = input("Enter name: ")
    serial = generate_serial(user_input)
    print(f"Serial: {serial}")