source_code: import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.OutputStream;
  import java.io.PrintWriter;
  import java.util.StringTokenizer;
  
  public class CF {
  
      public static void main(String[] args) throws IOException {
          InputStream inputStream = System.in;
          OutputStream outputStream = System.out;
          InputReader in = new InputReader(inputStream);
          PrintWriter out = new PrintWriter(outputStream);
  
          int n = in.nextInt();
          if (n >= 0) {
              out.println(n);
          } else {
              int res = n;
              n = Math.abs(n);
  
              String s = String.valueOf(Math.abs(n));
              if (s.length() == 1) {
                  res = 0;
              } else {
                  res = Math.max(-Integer.parseInt(s.substring(0, s.length() - 1)), res);
                  res = Math.max(-Integer.parseInt(s.substring(0, s.length() - 2) + s.charAt(s.length() - 1)), res);
              }
  
              out.println(res);
          }
  
          out.close();
      }
  }
  
  class InputReader {
      public BufferedReader reader;
      public StringTokenizer tokenizer;
  
      public InputReader(InputStream stream) {
          reader = new BufferedReader(new InputStreamReader(stream));
          tokenizer = null;
      }
  
      public String next() {
          while (tokenizer == null || !tokenizer.hasMoreTokens()) {
              try {
                  tokenizer = new StringTokenizer(reader.readLine());
              } catch (IOException e) {
                  throw new RuntimeException(e);
              }
          }
          return tokenizer.nextToken();
      }
  
      public int nextInt() {
          return Integer.parseInt(next());
      }
  
  }