using System;

public class Program

{

    public static void Main()

    {

        int counter_a=0,counter_b=0,a=0,b=0;

        string any="no";

        Console.Write("Hay nhap mot so bat ky: ");

        int x = Convert.ToInt32(Console.ReadLine());

        for (int i=1; i<x;i++)              //xet a tu 1 den x

        {

            counter_a=0;

            a=0;

            for (int i1=2; i1<=i/2;i1++)        //tim 1 so nguyen to va gan' vao a

            {

                if (i%i1==0) counter_a++;               

            }

            if (counter_a==0) a=i;

            for (int j =1; j<x; j++)             //xet b tu 1 den x

            {

                counter_b=0;

                b=0;

                for (int j1=2; j1<=j/2;j1++)    //tim 1 so nguyen to va gan' vao b

                {

                    if(j%j1==0) counter_b++;

                }

                if (counter_b==0) b=j;

                if ((a+b==x)&&(a<b))    { Console.WriteLine("{0} = {1} + {2}",x,a,b); any="yes"; }

                }

        }

        if (any=="no") Console.WriteLine("So vua nhap khong the duoc bieu dien bang tong cua hai so nguyen to!");

    }   

}

​

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