import system'routines;
import extensions;
import extensions'text;

singleton rotConvertor
{
    char convert(char ch)
    {
        if (($97 <= ch && ch <= $109) || ($65 <= ch && ch <= $77))
        {
            ^ (ch.toInt() + 13).toChar()
        };
        if (($110 <= ch && ch <= $122) || ($78 <= ch && ch <= $90))
        {
            ^ (ch.toInt() - 13).toChar()
        };

        ^ ch
    }

    string convert(string s)
        = s.selectBy:(ch => rotConvertor.convert(ch)).summarize(new StringWriter());
}

public program()
{
    if (program_arguments.Length > 1)
    {
        console.printLine(rotConvertor.convert(program_arguments[1]))
    }
}