source_code: import java.io.InputStreamReader;
  import java.io.IOException;
  import java.text.BreakIterator;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Map;
  import java.util.PriorityQueue;
  import java.util.Queue;
  import java.util.Scanner;
  import java.io.BufferedReader;
  import java.io.OutputStream;
  import java.io.PrintWriter;
  import java.util.StringTokenizer;
  import java.io.InputStream;
  
  public class palin {
  	public static void main(String[] args) {
  		InputStream inputStream = System.in;
  		OutputStream outputStream = System.out;
  		InputReader in = new InputReader(inputStream);
  		PrintWriter out = new PrintWriter(System.out);
  		Scanner scan = new Scanner(System.in);
  		TaskC solver = new TaskC();
  		solver.solve(1, in, out);
  		out.close();
  	}
  }
  
  class TaskC {
  	public void solve(int testNumber, InputReader in, PrintWriter out) {
  		int n = in.nextInt();
  		if (n >= 0) {
  			out.print(n);
  			return;
  		}
  		if (n / 10 >= (n / 100) * 10 + n % 10) {
  			out.print(n / 10);
  			return;
  		}
  		out.print((n / 100) * 10 + n % 10);
  	}
  }
  
  class InputReader {
  	BufferedReader br;
  	StringTokenizer st;
  
  	public InputReader(InputStream in) {
  		br = new BufferedReader(new InputStreamReader(in));
  		st = null;
  	}
  
  	public String next() {
  		while (st == null || !st.hasMoreTokens()) {
  			try {
  				st = new StringTokenizer(br.readLine());
  			} catch (IOException e) {
  				throw new RuntimeException(e);
  			}
  		}
  		return st.nextToken();
  	}
  
  	public int nextInt() {
  		return Integer.parseInt(next());
  	}
  
  	public long nextLong() {
  		return Long.parseLong(next());
  	}
  
  	public double nextDouble() {
  		return Double.parseDouble(next());
  	}
  }