OCC '19 S2 - Rimuru's Number Game

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Points: 5
Time limit: 1.0s
Memory limit: 64M

Problem types
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It's Pookmeister's birthday, and Rimuru wants to give him a gift. Knowing that he loves the numbers 2 and 3, Rimuru wants to know how many different numbers less than or equal to N that only consist of digits that are either 2 or 3.


  1. (20 points) N \le 10^5
  2. (80 points) No additional constraints.

Input Specification

A single integer N (3 \le N \le 10^{18}).

Output Specification

The answer to the problem, on a single line.

Sample Input 1


Sample Output 1


Explanation for Sample 1

The only two numbers are 2 and 3.

Sample Input 2


Sample Output 2


Explanation for Sample 2

The only valid numbers are 2, 3, 22, 23, 32 and 33.


  • -5
    jaydenchu2003  commented on Feb. 11, 2020, 10:04 p.m.

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    • 2
      CubixularHelix  commented on Sept. 26, 2020, 10:57 p.m.

      You don't need to check every number. Consider the implications of the numbers only having the digits 2 and 3.