source_code: import java.io.BufferedReader;
  import java.io.BufferedWriter;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.OutputStreamWriter;
  import java.io.PrintWriter;
  import java.util.StringTokenizer;
  
  
  public class TaskA implements Runnable {
  	
  	@Override
  	public void run() {
  		InputReader in = new InputReader(System.in);
  		PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
  		int n = in.readInt();
  		if (n > 0) {
  			out.println(n);
  		}
  		else {
  			int nn = -n;
  			int x = nn/10;
  			int lastDigit = nn%10;
  			int y = 10*(x/10) + lastDigit;
  			x = -x;
  			y = -y;
  			out.println(x > y ? x : y);
  		}
  		out.flush();
  	}
  
  	public static void main(String[] args) {
  		new TaskA().run();
  	}
  	
  	private 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 readInt() {
  	    	return Integer.parseInt(next());
  	    }
  	    
  	}
  
  }
  