Hexadecimal's Numbers

题面翻译

输入n，输出1-n的自然数中各数位只包含0和1的数的个数。 Translated by @Lolierl

题目描述

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.

输入格式

Input data contains the only number $n$ ( $1<=n<=10^{9}$ ).

输出格式

Output the only number — answer to the problem.

样例 #1

样例输入 #1

10

样例输出 #1

2

提示

For $n$ = 10 the answer includes numbers 1 and 10.