source_code: import java.io.*;
  
  public class Main {
  	
  	public static void main(String[] args) throws Exception {
  		
  		int n = nextInt();
  		String nn = Integer.toString(n);
  		if(n >= 0){
  			println(n);
  		} else {
  			println(Math.max(Integer.parseInt(nn.substring(0,nn.length() - 1)), Integer.parseInt(nn.substring(0, nn.length() - 2) + nn.charAt(nn.length() - 1))));
  		}
  	}
  	
  	private static PrintWriter out =  new PrintWriter(System.out);
  	private static BufferedReader inB = new BufferedReader(new InputStreamReader(System.in));	
  	private static StreamTokenizer in = new StreamTokenizer(inB);
  	
  	private static void exit(Object o) throws Exception {
  		out.println(o);
  		out.flush();
  		System.exit(0);
  	}
  	private static void println(Object o) throws Exception{
  		out.println(o);
  		out.flush();
  	}
  	private static void print(Object o) throws Exception{
  		out.print(o);
  		out.flush();
  	}
  	private static long nextLong() throws Exception {
  		in.nextToken();
  		return (long)in.nval;
  	}  
  	private static int nextInt() throws Exception {
  		in.nextToken();
  		return (int)in.nval;
  	}  
  	private static String nextString() throws Exception {
  		in.nextToken();
  		return in.sval;        
  	}
  	
  } 