source_code: import java.io.BufferedOutputStream;
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  
  public class Main {
  
  	public static void main(String [] args ) {
  		try{
  			String str;			
  			BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  			BufferedOutputStream bos = new BufferedOutputStream(System.out);
  			String eol = System.getProperty("line.separator");
  			byte [] eolb = eol.getBytes();
  			byte[] spaceb= " ".getBytes();
  
  
  			str  = br.readLine();
  
  			int n = Integer.parseInt(str);
  			int ans = 0;
  			if(n>=0) {
  				ans = n;
  			} else {
  				 if ( str.length()==2) {
  					if(str.charAt(0)!='-') {
  						int a  =Integer.parseInt(str.substring(0,1));
  						int b = Integer.parseInt(str.substring(1,2));
  						ans = Math.max(a, b);
  					} else {
  						ans = Integer.parseInt(str.substring(1,2));
  					}
  				} else {
  					String s1 = str.substring(0,str.length()-2).concat(str.substring(str.length()-2,str.length()-1));
  					String s2 = str.substring(0,str.length()-2).concat(str.substring(str.length()-1,str.length()));
  					int a = Integer.parseInt(s1);
  					int b = Integer.parseInt(s2);
  					ans = Math.max(a, b);
  				}
  			}
  			bos.write(new Integer(ans).toString().getBytes());
  			bos.write(eolb);
  			bos.flush();
  		}  catch(IOException ioe) {
  			ioe.printStackTrace();
  		}
  	}
  }
  