[BOJ] 백준 2960 에라토스테네스의

[문제]

https://www.acmicpc.net/problem/2960

 

[소스 코드]

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));
		StringTokenizer st = new StringTokenizer(br.readLine());
		int n = Integer.parseInt(st.nextToken());
		int k = Integer.parseInt(st.nextToken()) - 1;
		boolean[] num = new boolean[n+1];
		List<Integer> list = new ArrayList<>();
		for(int i=2;i<=n;i++) {
			if(num[i]) 
				continue;
			list.add(i);
			num[i] = true;
			for(int j=i*i;j<=n;j+=i) {
				if(!num[j])
					list.add(j);
				num[j] = true;
			}
		}
		System.out.println(list.get(k));
	}
}