codeforce 9C（Hexadecimal's Numbers）

来   看谁的代码短

C. Hexadecimal's Numbers

time limit per test

1 second

memory limit per test

64 megabytes

input

standard input

output

standard output

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 ≤ 109).

Output

Output the only number — answer to the problem.

Sample test(s)

input

10

output

2

Note

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

#include <iostream>
using namespace std;
int n;
int ans;
void f(int x){
   if(x>n) return ;
   ans++;
   f(x*10);
   f(x*10+1);
}
int main(){
   cin>>n;
   ans=0;
   f(1);
   cout<<ans<<endl;
}