How Many Trees?

import java.util.*;
import java.math.*;
public class Main
{
public static void main(String []args)
{
Scanner cin=new Scanner(System.in);
int i,n;
while(cin.hasNext())
{
n=cin.nextInt();
BigInteger s1 = BigInteger.valueOf(1);
BigInteger s2 = BigInteger.valueOf(1);
for(i=1;i<=n;i++)
{
s1=s1.multiply(BigInteger.valueOf(2*n-i+1));
s2=s2.multiply(BigInteger.valueOf(i));
}
s1=s1.divide(BigInteger.valueOf(n+1));
System.out.println(s1.divide(s2));
}
}
}