Runtime error (NZRC) in Java

Hi ,
can you please tell me what is wrong with this code . This is the java code for
‘Bytelandian gold coins’ practice problems . My output is correct and within the time limit also. But not sure why I am getting Runtime error

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;

class GoldCoin {

static HashMap<Long,Long> cached = new HashMap<Long,Long>();
public static void main(String[] args)
{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
ArrayList b = new ArrayList();

	int count=0;
	String row;
			while(count<10)
			{
				try {
					row=br.readLine();
				
				if(isInteger(row))
					{
						b.add(Long.parseLong(row));
						count++;
					}
				else
					break;
			}
				
			 catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			}
			
		for (Long k:b) 
	{	
		System.out.println(getDollar(k));
	   
	}
	
}

static long getDollar(Long k)
{
	long m;
	if(cached.containsKey(k))
	return cached.get(k);
	else
		 m=(k > (k/2 +k/3+k/4))? k :(getDollar(k/2) +getDollar(k/3)+getDollar(k/4));
	cached.put(k,m);
	return m;
	
	
}

static boolean isInteger(String s) {
    try { 
        Long.parseLong(s); 
    } catch(NumberFormatException e) { 
        return false; 
    }
    // only got here if we didn't return false
    return true;
}

}

//