def main():
    j = input()
    if j[0] != "1":
        print(-1)
        return
    n = 0
    if (len(j[1:]) == 0) :
        print(-1)
        return
    for v in j[1:]:
        if v == "3":
            n += 1
        elif v != "3":
            print(-1)
            return
    print(n)


main()