private void ShowDigits(string input)
        {
            var displayedNumber = screen.Content.ToString().Count();

            if (screen.Content.ToString() == "0")
            {
                screen.Content = "";
            }

            if (input == "=" &&
                listOfInput.Any())
            {
                var screenContent = screen.Content.ToString().Replace("X", "*").Replace("mod", "#");

                if (screen.Content.ToString().Contains("sqrt"))
                {
                    screenContent = screenContent.Replace("sqrt", "sqrt(") + ")";
                }

                if (input == "=")
                {
                    if (CurrentMenu == OperationsUnit.Standard)
                    {
                        screen.Content = CalculateOperations.GetResult(screenContent);
                    }

                    else if (CurrentMenu == OperationsUnit.Decimal)
                    {
                        var inputAsint = Convert.ToInt32(screen.Content);
                        screen.Content = BinaryOperation.GetResult(inputAsint, ConvertionMethod);
                    }

                    else if (CurrentMenu == OperationsUnit.Percentage)
                    {
                        screen.Content = PercentOperation.GetResult(screenContent, SelectPercent);
                    }
                    else if (CurrentMenu == OperationsUnit.Weight)
                    {
                        screen.Content = WeightOperations.GetResult(screenContent, FromWeightUnit, ToWeightUnit);
                    }
                    else if (CurrentMenu == OperationsUnit.Temperature)
                    {
                        screen.Content = TemperatureOperations.GetResult(screenContent, TemperatureUnit);
                    }
                    else if (CurrentMenu == OperationsUnit.Length)
                    {
                        screen.Content = LengthOperations.GetResult(screenContent, FromLengthUnit, ToLUnit);
                    }
                    else if (CurrentMenu == OperationsUnit.File)
                    {
                        screen.Content = FileOperations.GetResult(screenContent, FromFileUnit, ToFileUnit);
                    }
                    else if (CurrentMenu == OperationsUnit.Time)
                    {
                        screen.Content = TimeOperations.GetResult(screenContent, FromTimeUnit, ToTimeUnit);
                    }
                }

                listOfInput.Clear();
            }

            else if (displayedNumber >= 13)
            {
                MessageBox.Show("Maximum Input exceed", "Input limit", MessageBoxButton.OK, MessageBoxImage.Stop);
            }

            else
            {
                listOfInput.Add(input);
                screen.Content += input.ToString();
            }
        }