Hexadecimal's Numbers

• Problem 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<109).
  
  Output
  Output the only number answer to the problem.
  "
  

• CODING ARENA

• #include<stdio.h>

  int tot=0;

  
  

  void getNum(long long num,long long n)

  {

  if(num>n)

  return;

  tot++;

  num=num*10;

  getNum(num+1,n);

  getNum(num,n);

  }

  int main()

  {

      long long n;

      scanf("%lld",&n);

      getNum(1,n);

      printf("%d",tot);

      return 0;

  }

• Test Case 1

  
  Input (stdin)

  10
  
  

  Expected Output

  2

• Test Case 2

  
  Input (stdin)

  20
  
  

  Expected Output

  3