import java.math.BigInteger;
import java.net.*;
import java.io.*;

public class FibServer {

    // This is the naive approach. We should do this with
    // a thread pool, and I may add that later; but that would
    // be so much easier in Java 5, I'll do the Java 5 solution
    // first.
    public static void main(String[] args) throws IOException {
        
        ServerSocket ss = new ServerSocket(8234);
        while (true) {
            Socket s = ss.accept();
            Responder r = new Responder(s);
            r.start();
        }
        
    }
    
    private static class Responder extends Thread {

        private Socket socket;
        
        Responder(Socket s) {
            this.socket = s;
        }
        
        
        public void run() {
            try {
                InputStream in = socket.getInputStream();
                BufferedReader reader = new BufferedReader(new InputStreamReader(in, "US-ASCII"));
                String s = reader.readLine();
                int input = Integer.parseInt(s);
                BigInteger result = fib(input);
                OutputStream out = socket.getOutputStream();
                String output = result.toString();
                out.write(output.getBytes("US-ASCII"));
                out.write('\r');
                out.write('\n');
                out.flush();
            } 
            catch (Exception ex) {
               // no big deal; or we could write an error message.
               // If so, I'd wanted a nested try block above. 
            }
            finally {
                try {
                    socket.close();
                } 
                catch (IOException ex) {
                  //nothing we can do  
                }
                
            }
            
        }

        
        private BigInteger fib(int input) {
            
            if (input < 0) {
                throw new IllegalArgumentException("Negative number");
            }
            BigInteger low = BigInteger.ZERO;
            BigInteger high = BigInteger.ONE;
            
            for (int i = 0; i < input; i++) {
                BigInteger temp = high;
                high = high.add(low);
                low = temp;
            }
            return low;
        }
        
    }
   
    
}