1.

import java.util.Scanner;

/**
* FWP, Ausgewählte Probleme aus dem ACM Programming Contest, SS10
* Problem: 369 - Combinations
* Link: http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=5&page=show_problem&problem=305
*
* @author Siegfried Ippisch
* @version 1.0
*
* Method : -
* Status : Accepted
* Runtime: 0.684
*/
public class Combinations {

public static void main(String[] args){
Scanner in = new Scanner(System.in);

long n = in.nextLong();
long m = in.nextLong();

while(n != 0 || m != 0){
System.out.printf("%d things taken %d at a time is %d exactly.\n",n,m,f(n,m));
n = in.nextLong();
m = in.nextLong();
}

in.close();
}

public static int f(long n, long m){
double res = 1;
for(long i=0; i<m; i++){
res = res * (n-i);
res = res / (i+1);
}
return (int)(res+0.5);
}
}

2.



package acm_369_combinations;

import java.util.Scanner;

/**
 * FWP, AusgewŠhlte Probleme aus dem ACM Programming Contest, SS10 
 * Problem: acm_369_combinations
 * Link: http://uva.onlinejudge.org/index.php?option=com_onlinejudge&page=show_problem&problem=305&Itemid=8
 * 
 * @author Martin Lambeck
 * @version 1.0, 18.08.2010
 * 
 * Method : adhoc
 * Status : Accepted
 * Runtime: 0.780
 */


public class Main
{
	static Scanner sc = new Scanner(System.in);

	public static void main(String... args)
	{
		while (testcase())
			;
	}

	public static boolean testcase()
	{
		
		int n = sc.nextInt();
		int m = sc.nextInt();

		if ((n == 0) && (m==0))
			return false;
		
		double b = 1.0;
		
		double mi = 1.0;
		int ni = n;
		
		int mmax = Math.min(m, n-m);
		
		for (int i = 0; i < mmax; i++)
		{
			double v = ni / mi;
			
			b *= v;
			
			ni--;
			mi++;
		}

		System.out.printf("%d things taken %d at a time is %d exactly.%n",n, m, (int) (b+0.001));

		return true;
	}
}