private static void Main()
{
const string input = "2x^2+3x";
var del = MathEvaluator.Parse(input);
Console.WriteLine(del.DynamicInvoke(2));
Console.ReadKey();
}
private static void Main()
{
string middle = Console.ReadLine();
var del = MathEvaluator.Parse(middle);
Console.WriteLine(del.DynamicInvoke(5));
Console.ReadKey();
}