Hexadecimal's Numbers
时间限制:C/C++/Rust/Pascal 1秒,其他语言2秒
空间限制:C/C++/Rust/Pascal 64 M,其他语言128 M
64bit IO Format: %lld

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.

输入描述:

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

输出描述:

Output the only number — answer to the problem.

示例1

输入

复制
10

输出

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2

备注:

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