source_code: import java.io.*;
  
  public class Main {
    public static void main(String args[]) throws IOException {
      BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
      String line = stdin.readLine();
      int n = Integer.parseInt(line);
      
      if (n >= 0) {
        System.out.println(n);
      } else if (n > -10) {
        System.out.println(0);
      } else {
        String sa = line.substring(0, line.length() - 1);
        int a = Integer.parseInt(sa);
        String sb = line.substring(0, line.length() - 2) + line.charAt(line.length() - 1);
        int b = Integer.parseInt(sb);
        System.out.println(Math.max(a, b));
      }
    }
  }
  