source_code: /*
   * To change this template, choose Tools | Templates
   * and open the template in the editor.
   */
  
  import java.io.*;
  import java.util.*;
  
  /**
   *
   * @author N-AssassiN
   */
  public class Main {
  
      private static BufferedReader reader;
      private static BufferedWriter out;
      private static StringTokenizer tokenizer;
      //private final static String filename = "filename";
  
      private static void init(InputStream input, OutputStream output) {
          reader = new BufferedReader(new InputStreamReader(input));
          out = new BufferedWriter(new OutputStreamWriter(output));
          //reader = new BufferedReader(new FileReader(filename + ".in"));
          //out = new BufferedWriter(new FileWriter(filename + ".out"));
          tokenizer = new StringTokenizer("");
      }
  
      private static String nextLine() throws IOException {
          return reader.readLine();
      }
  
      private static String next() throws IOException {
          while (!tokenizer.hasMoreTokens()) {
              tokenizer = new StringTokenizer(nextLine());
          }
          return tokenizer.nextToken();
      }
  
      private static int nextInt() throws IOException {
          return Integer.parseInt(next());
      }
  
      private static long nextLong() throws IOException {
          return Long.parseLong(next());
      }
  
      private static double nextDouble() throws IOException {
          return Double.parseDouble(next());
      }
  
      /**
       * @param args the command line arguments
       */
      public static void main(String[] args) throws IOException {
          init(System.in, System.out);
          int n = nextInt();
          //long startTime = System.currentTimeMillis();
          if (n > 0) {
              out.write(n + "\n");
          } else {
              String s = n + "";
              String s2 = s.substring(0, s.length() - 1);
              String s3 = s.substring(0, s.length() - 2) + s.charAt(s.length() - 1);
              int a = Integer.parseInt(s2);
              int b = Integer.parseInt(s3);
              int ans = Math.max(a, b);
              out.write(ans + "\n");
          }
          //long runTime = System.currentTimeMillis() - startTime;
          //out.write(runTime + "\n");
          out.flush();
      }
  }