using System;

public class Program

{

    public static void Main()

    {

        int x = 20;

        for(int i=2;i<x;i++)

        {

            int count = 0;

            for(int j=2;j<= i/2;j++)

            {

                if(i%j == 0)

                {

                    count++;

                }

            }

            if(count < 1)

                Console.WriteLine(i);

        }

    }

}