One beautiful July morning a terrible thing happened in Mainframe: a mean virus Megabyte somehow got access to the memory of his not less mean sister Hexadecimal. He loaded there a huge amount of n different natural numbers from 1 to n to obtain total control over her energy.

But his plan failed. The reason for this was very simple: Hexadecimal didn't perceive any information, apart from numbers written in binary format. This means that if a number in a decimal representation contained characters apart from 0 and 1, it was not stored in the memory. Now Megabyte wants to know, how many numbers were loaded successfully.

Input

Input data contains the only number n (1 ≤ n ≤ 109).

Output

Output the only number — answer to the problem.

Examples

Input

10


Output

2

Note

For n = 10 the answer includes numbers 1 and 10.
__author__ = 'Darren'


def solve():
    str_n = input()
    len_n = len(str_n)
    count = 0
    ord_1, ord_2 = ord('1'), ord('2')
    for i in range(len_n):
        if ord(str_n[i]) >= ord_2:
            count += 1 << (len_n - i)
            break
        elif ord(str_n[i]) == ord_1:
            count += 1 << (len_n - i - 1)
        else:
            pass
    else:
        count += 1
    print(count - 1)


if __name__ == '__main__':
    solve()