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• 题目来源
• 评测方式 RemoteJudge
• 标签 枚举,暴力 进制 递归 队列
• 难度 普及-
• 时空限制 1000ms / 64MB
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## 题意翻译

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.

## 输入输出格式

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.

## 输入输出样例

输入样例#1： 复制
10

输出样例#1： 复制
2

## 说明

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

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