source_code: import static java.util.Arrays.deepToString;
  
  import java.awt.datatransfer.StringSelection;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.math.BigInteger;
  import java.util.StringTokenizer;
  
  public class Main {
  
      static void solve() throws IOException {
          int n = nextInt();
          if (n >= 0) {
              System.out.println(n);
          } else {
              String string = String.valueOf(n);
              int v1 = Integer.valueOf(string.substring(0, string.length() - 1));
              int v2 = Integer.valueOf(string.substring(0, string.length() - 2)
                      + string.charAt(string.length() - 1));
              if (v1 >= v2) {
                  System.out.println(v1);
              } else {
                  System.out.println(v2);
              }
          }
          
      }
  
      public static void main(String[] args) throws Exception {
          reader = new BufferedReader(new InputStreamReader(System.in));
          writer = new PrintWriter(System.out);
  
          setTime();
          solve();
          printTime();
          printMemory();
  
          writer.close();
      }
  
      static BufferedReader reader;
      static PrintWriter writer;
      static StringTokenizer tok = new StringTokenizer("");
      static long systemTime;
  
      static void debug(Object... o) {
          System.err.println(deepToString(o));
      }
  
      static void setTime() {
          systemTime = System.currentTimeMillis();
      }
  
      static void printTime() {
          System.err.println("Time consumed: "
                  + (System.currentTimeMillis() - systemTime));
      }
  
      static void printMemory() {
          System.err.println("Memory consumed: "
                  + (Runtime.getRuntime().totalMemory() - Runtime.getRuntime()
                          .freeMemory()) / 1000 + "kb");
      }
  
      static String next() {
          while (!tok.hasMoreTokens()) {
              String w = null;
              try {
                  w = reader.readLine();
              } catch (Exception e) {
                  e.printStackTrace();
              }
              if (w == null)
                  return null;
              tok = new StringTokenizer(w);
          }
          return tok.nextToken();
      }
  
      static int nextInt() {
          return Integer.parseInt(next());
      }
  
      static long nextLong() {
          return Long.parseLong(next());
      }
  
      static double nextDouble() {
          return Double.parseDouble(next());
      }
  
      static BigInteger nextBigInteger() {
          return new BigInteger(next());
      }
  }