1453: C. Hexadecimal's Numbers
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Description
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 $n\ (1≤n≤10^9)$.
Output
Output the only number − answer to the problem.
Sample 1 Input
10
Sample 1 Output
2
For n = 10 the answer includes numbers 1 and 10.