UVA Problem ID 10007 (Count the Trees)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.math.BigInteger;


public class Main {
 public static void main (String args[]) throws IOException
 {
  BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
  StringBuilder sb=new StringBuilder(10000);
  
  while(true)
  {
   int n=Integer.parseInt(br.readLine().trim());
   if(n==0)
    break;
   sb.append(factorial(new BigInteger((2*n)+"")).divide(factorial(new BigInteger((n+1)+"")))+"\n");
  }
  System.out.print(sb);
 }
 public static BigInteger factorial(BigInteger n)
 {
  if(n.intValue()==0 || n.intValue()==1)
   return BigInteger.ONE;
  else
  {
   return n.multiply(factorial(n.subtract(BigInteger.ONE)));
  }
 }
}