[백준] 1418번 k-세준수 (silver 5

import java.io.*;
import java.util.*;
public class Main{
    public static void main(String[] args)throws IOException{
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw=new BufferedWriter(new OutputStreamWriter(System.out));
        int n=Integer.parseInt(br.readLine());
        int[] num=new int[n+1];
        int answer=1;
        for(int i=2; i<n+1; i++){
            if(num[i]!=0){
                continue;
            }
            for(int j=i+i; j<n+1; j+=i){
                num[j]=i;
            }
            num[i]=i;
        }
        int k=Integer.parseInt(br.readLine());
        for(Integer e: num){
            if(e!=0 && e<=k){
                answer++;
            }
        }
        bw.write(answer+"");
        bw.flush();
    }
}