Poj Solution 1306

http://poj.org/problem?id=1306

//* @author ������<hongxp11@163.com>
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.Scanner;


public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(true)
        {
            int n = in.nextInt();
            int m = in.nextInt();
            int m1 = m;
            BigInteger sum1 = new BigInteger("1");
            BigInteger sum2 = new BigInteger("1");
            BigDecimal a;
            if(n == 0 && m == 0)
                break;
            if(m > n/2)
            {
                m = n - m;
            }
            for(int i = 0; i< m; i++)
            {
                sum1 = sum1.multiply(new BigInteger(String.valueOf(n-i))); 
            }
            for(int i = 0; i< m; i++)
            {
                sum2 = sum2.multiply(new BigInteger(String.valueOf(i+1)));
            }
            System.out.println(n + " things taken " + m1 +" at a time is " 
                    + sum1.divide(sum2) +" exactly.");
        }
    }

}