ForC#1

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {

            int a = Convert.ToInt32(Console.ReadLine());
            int b = Convert.ToInt32(Console.ReadLine());

            Console.WriteLine(Func(a, b));

            if(Func(a, b) == 1)
            {
                Console.WriteLine("Простое!");
            }
            else
            {
                Console.WriteLine("Не простое!!");
            }

            Console.ReadKey();
        }

        public static int Func(int k, int n)
        {
            if( k * k > n)
            {
                return 1;
            }
            if(n % k == 0)
            {
                return 0;
            }

            return Func(n, k++);
        }
    }
}