Bishops nzec

Hi..
Im getting a Runtime Error NZEC:
And i dont understand y>>

import java.io.*;
import java.math.*;
public class Main {
    /**
 * @param args
 */
public static void main(String[] args) throws IOException
{
	String s=(new DataInputStream(System.in)).readLine();
	while(!s.equals(""))
	{
		if(s.equals("1"))
		{
			System.out.println("1");
			s=(new DataInputStream(System.in)).readLine();
			continue;
		}
		BigInteger q=new BigInteger(s);
		System.out.println(q.multiply(new BigInteger("2")).subtract(new BigInteger("2")));
		s=(new DataInputStream(System.in)).readLine();
	}
	}
	// TODO Auto-generated method stub

}

plss help