import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;

public class Main {
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final long n = sc.nextLong();
		
		long count = 0;
		
		long curr = 1000000001;
		long base = curr;
		while(curr <= n){
			for(int i = 0; i < 9; i++){
				if(curr > n){ break; }
				
				count++;
				curr += base;
			}
			curr += base;
			
			//System.out.println(curr + " " + count);
			base = curr;
		}
		
		System.out.println(count);
	}
}