package hello;


import java.util.Scanner;



public class Lottery 
{
  public static void main(String[] args)
    {	
		Scanner in= new Scanner(System.in);
		 System.out.println("你要选多少个数？");
		 int a = in.nextInt();
		 
		 System.out.println("总共有多少个数？");
		 double b = in.nextInt();
		 
		 int lotteryodds = 1;
		 for(int c=1;c<=a;c++)
			 lotteryodds*=(b-c+1)/c;
		 System.out.println("你中奖概率是 "+lotteryodds+" 分之一！！！！");
			 
			
	    	
	 }
}