import java.util.*;
import java.io.*;

public class Main {
    
    public static Scanner sc = new Scanner(System.in);
    public static PrintWriter pw = new PrintWriter(System.out);
    
    public static void main(String[] args) {
        
        int t = 1;
        while( t > 0 ) {
            solve();
            t--;
        }
        
        pw.flush();
        
    }
    
    static void solve() {
        
        long N = sc.nextLong();
        long low = 0;
        long high = 100000;
        long mid = 0;
        while( low < high ) {
            mid = (high+low)/2;
            String s = Long.toString(mid);
            long ttv = Long.valueOf(s+s+s);
            if( ttv <= N ) {
                low = mid+1;
            }else {
                high = mid;
            }
        }
        
        pw.println(low-1);
        
    }
    
}