Hexadecimal's Numbers
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
10
输出样例 #1
2
说明
For $ n $ = 10 the answer includes numbers 1 and 10.