n = input('Input your credit card number: ')



def legitcheck(n):
    l = 0
    s1 = []
    s2 = []
    if len(n) == 13 or len(n) == 16:

        for i in range(len(n) - 2, -1, -2):
            s = int(n[i]) * 2
            if s > 10 and not s == 10:
                l = 1 + s % 10
                s1.append(l)
            if s == 10:
                s1.append(1)
            if s < 10:
                s1.append(s)
        summa1 = sum(map(int, s1))

        for i in range(len(n) - 1, -1, -2):
            s2.append(n[i])
        summa2 = sum(map(int, s2))

        grand_summa = summa1 + summa2

        if grand_summa % 10 == 0:
            print('Your card is valid')
        else:
            print('**fake card is being detected**')
    else:
        print("*invalid card*")


legitcheck(n)