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 ans = 0;
        for( long d = 1; d <= 100000; d++,ans++ ) {
            long ttv = Long.valueOf(Long.toString(d)+Long.toString(d)+Long.toString(d));
            if( ttv > N ) break;
        }
        
        pw.println(ans);
        
    }
    
}