hdu Game of Connections

 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             else
22                 System.out.println(c[N]);
23         }
24     }
25 }