/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package ktltbai9;

import java.util.Scanner;

/**
 *
 * @author Admin
 */
public class bai9 {

    public static void main(String[] args) {
        int m = 0;
        while (true) {
            System.out.println("Nhập số: ");
            int n = nhapso();
            switch (n) {
                case 1:
                    m = nhapso();
                    break;
                case 2:
                    sntVongLap(m);
                    break;
                case 3:
                    sntDeQuy(m);
                    break;
                case 4:
                    System.exit(0);
                default:
                    continue;
            }
        }

    }

    public static int nhapso() {
        int n;
        try {
            n = Integer.parseInt(new Scanner(System.in).nextLine());
        } catch (NumberFormatException e) {
            System.out.println("Nhập lại đúng định dạng");
            return nhapso();
        }
        return n;
    }

    private static void sntDeQuy(int n) {
        if (n < 2) {
            return;
        }
        if (ktraSNT(n)) {
            System.out.println(n);
            sntDeQuy(n - 1);
        } else {
            sntDeQuy(n - 1);
        }
    }

    private static boolean ktraSNT(int n) {
        if (n < 2) {
            return false;
        } else if (n == 2 || n == 3) {
            return true;
        }

        for (int i = 2; i <= Math.sqrt((double) n); i++) {
            if (n % i == 0) {
                return false;
            }
        }
        return true;
    }

    private static void sntVongLap(int n) {

        while (true) {
            if (n < 2) {
                return;
            }
            if (ktraSNT(n)) {
                System.out.println(n);
                n--;
            } else {
                n--;
            }
        }
    }
}