static void Main(string[] args) { var tableOnlyNumbers = new List <List <int> >(); string path = @"C:\Users\home\Desktop\Zadanie\numbers.txt"; string[] readText = File.ReadAllLines(path); bool validation = false; string inputEquasion = ""; Console.WriteLine($"Loaded numbers are \n {readText[0]} \n {readText[1]}"); // converting input to table with numeric values in cells var readTextConvertedToTable = Helper.ConvertingInput(readText); Helper.ConvertingTableToNumbersOnly(readTextConvertedToTable); // validation while (!validation) { inputEquasion = Console.ReadLine(); validation = Validation.Validate(inputEquasion, readTextConvertedToTable); if (!validation) { Console.WriteLine("Please enter new equasion"); } } ; // converting input to form that can be understood by expresionTree builder inputEquasion = inputEquasion.Replace(" ", string.Empty); var numericInput = Helper.ConvertEquationsToNumericEquations(inputEquasion, readTextConvertedToTable); var postfix = PostfixConverter.infixToPostfix(numericInput); // building and evaluatig expression tree var tree = ExpressionTree.ConstructTree(postfix); var eval = ExpressionTree.EvalTree(tree); Console.WriteLine($"Your result is {eval}"); Console.ReadLine(); }