UVA - 10303 - How Many Trees?

//Catalan Number problem
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));
        StringBuffer sb = new StringBuffer("");
        String m="";
        BigInteger []catlan=new BigInteger[1001];
        BigInteger []fact=new BigInteger[2001];
        fact[0]=BigInteger.ONE;
        fact[1]=BigInteger.ONE;
        for(int i=2;i<fact.length;i++){
            fact[i]=fact[i-1].multiply(BigInteger.valueOf(i));
        }
        for(int i=0;i<catlan.length;i++){
            catlan[i]=fact[2*i].divide(fact[i+1].multiply(fact[i]));
        }
        while((m=br.readLine())!=null) {
            int n=Integer.parseInt(m);
            sb.append(catlan[n]).append("\n");
        }
        System.out.print(sb);
    }

}