using System;

public class Program

{

    public static bool IsSimple(int num){

        for(int i = 2; i <= Math.Sqrt(num); i++)

        {

            if(num % i == 0)

            {

                return false;

            }

        }

        return true;

    }

    public static void Main()

    {

        for(int i = 1; i <= 20; i++)

        {

            Console.WriteLine(i.ToString() + ": " + IsSimple(i));

        }

    }

}