System.Console.WriteLine("Please input string :");
            string strTmp = System.Console.ReadLine();

            // judge the character ,please do it by yourself..

            char[] cTmp = new char[strTmp.Length -1];
            cTmp = strTmp.ToCharArray();
            string sTmp = "";
            char cTmp1 ;
            // Encrypt
            foreach(char c  in cTmp)
            {
                if(c + 3 == 'z')
                {
                    cTmp1 = 'z';
                }
                else if( c + 3 > 'z')
                {
                    cTmp1 =(char)( c - 23);
                }
                else
                {
                    cTmp1 =(char)(c+3);
                }
                sTmp += cTmp1;
            }
            System.Console.WriteLine("After Encrypt");
            System.Console.WriteLine(sTmp);