HDU How Many Trees?

import java.math.BigInteger;
import java.util.Scanner;

/**
* Created by ZUOYANBIN1 on 2017/9/18.
*/
public class Main {
static int n = 0;
static void solve(){
BigInteger ans = new BigInteger("1");
for(int i = 1; i <= n; i++){
ans = ans.multiply(new BigInteger(String.valueOf(4 * i - 2)))
.divide(new BigInteger(String.valueOf(i + 1)));
}
System.out.println(ans);
}
public static void main(String[] args){
Scanner in = new Scanner(System.in);
while(in.hasNext()){
n = in.nextInt();
solve();
}
}
}