source_code: import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.PrintWriter;
  import java.util.*;
  
  
  public class A {	
  	BufferedReader reader;
      StringTokenizer tokenizer;
      PrintWriter out;
      
  	public void solve() throws IOException {				
  		int N = nextInt();
  		if( N >= 0) {
  			out.println(N);
  			return;
  		}
  		
  		int ans = N/10;
  		int ans2 = N/100*10 + N%10;
  		out.println( Math.max(ans, ans2));
  		
  	}
  	
  	/**
  	 * @param args
  	 */
  	public static void main(String[] args) {
  		new A().run();
  	}
  	
  	public void run() {
          try {
              reader = new BufferedReader(new InputStreamReader(System.in));
              tokenizer = null;
              out = new PrintWriter(System.out);
              solve();
              reader.close();
              out.close();
          } catch (Exception e) {
              e.printStackTrace();
              System.exit(1);
          }
      }
  
      int nextInt() throws IOException {
          return Integer.parseInt(nextToken());
      }
  
      long nextLong() throws IOException {
          return Long.parseLong(nextToken());
      }
  
      double nextDouble() throws IOException {
          return Double.parseDouble(nextToken());
      }
  
      String nextToken() throws IOException {
          while (tokenizer == null || !tokenizer.hasMoreTokens()) {
              tokenizer = new StringTokenizer(reader.readLine());
          }
          return tokenizer.nextToken();
      }
  
  }
  