1 import java.math.BigInteger; 2 import java.util.Scanner; 3  4 public class Main { 5  6     public static void main(String args[]) { 7         Scanner cin = new Scanner(System.in); 8         BigInteger[] c = new BigInteger[101]; 9         c[1] = BigInteger.valueOf(1);10         c[2] = BigInteger.valueOf(2);11         for (int i = 3; i <= 100; i++) {12             BigInteger x1 = BigInteger.valueOf(4*i-2);13             BigInteger x2 = BigInteger.valueOf(i+1);14             c[i]=c[i-1].multiply(x1).divide(x2);15         }16     17         while (cin.hasNext()) {18             int N = cin.nextInt();19             if (N==-1)20                 break;21             else22                 System.out.println(c[N]);23         }24     }25 }