历届试题 幸运数

import java.util.Scanner;

public class Main {

    static int[] num = new int[110000];
    static int m;
    static int n;
    static int result = 0;

    public static void dfs(int index){
        int cnt = index;
        if(num[index] > n){
            return;
        }
        for(int i = index ; i < n ; i++){
            if((i+1) % num[index] != 0){
                num[cnt++] = num[i];
            }
        }
        dfs(index+1);
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in = new Scanner(System.in);
        m = in.nextInt();
        n = in.nextInt();
        for(int i = 0 ; i < n ; i++){
            num[i] = 2*i+1;
        }
        dfs(1);
        for(int i = 0 ; i < n ; i++){
            if(num[i] > m && num[i] < n){
                result++;
            }
        }
        System.out.println(result);
        in.close();
    }

}