_nＣ_rの計算

/****************************/
/* nＣrの計算               */
/*      coded by Y.Suganuma */
/****************************/
import java.io.*;

public class Test {
	public static void main(String args[])
	{
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		double sn, sr, snr;
		int n = 0, r = 0;
	/*
		 データの入力
	*/
		try {
			System.out.print("ｎの値は？ ");
			n = Integer.parseInt(in.readLine());
			System.out.print("ｒの値は？ ");
			r = Integer.parseInt(in.readLine());
		}
		catch (IOException ignored) {}
	/*
		 nＣrの計算と出力
	*/
		sn  = kaijo(n);
		sr  = kaijo(r);
		snr = kaijo(n-r);
		System.out.println("   " + n + "Ｃ" + r + "は＝" + sn/(sr*snr));
	}

	/**************************/
	/* ｍの階乗               */
	/*      m : データ        */
	/*      return : ｎの階乗 */
	/**************************/
	static double kaijo(int m)
	{
		double s;
		int i1;

		s = 1.0;
		for (i1 = 1; i1 <= m; i1++)
			s *= (double)i1;

		return s;
	}
}