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.
# -*- coding: utf-8 -*-
"""
Created on Thu Mar 12 11:52:12 2020

@author: akprasad
"""

def get_n_digit_binary(n):
    if n == 1:
        return ['0', '1']
    smaller = get_n_digit_binary(n-1)
    return ['0' + s for s in smaller] + ['1' + s for s in smaller]


def get_all_n_digit_binary(n):
    if n == 1:
        return ['1']
    smaller = get_all_n_digit_binary(n-1)
    return smaller + ['1' + s for s in get_n_digit_binary(n-1)]


if __name__ == '__main__':
    MAX = 10
    n = int(input())
    ndb = [int(x) for x in get_all_n_digit_binary(MAX)]
    found = False
    for i in range(len(ndb)):
        if ndb[i] > n:
            print(i)
            found = True
            break
    if not found:
        print(len(ndb))