from fire import Fire

def checksum(cardnumber: int):
    cardnumber = [int(i) for i in str(cardnumber)] 
    cardnumber.reverse()
    odd = [v for i, v in enumerate(cardnumber) if i % 2 == 0]
    even = [v for i, v in enumerate(cardnumber) if i % 2 != 0]

    even_sum = int()
    for i in even:
        dd = i * 2
        if dd > 9:
            even_sum += int(str(dd)[0]) + int(str(dd)[1])
        else:
            even_sum += dd


    return even_sum + sum(odd)
    

Fire(checksum)