static void Main() { Thread.CurrentThread.CurrentCulture = new CultureInfo("en-Us"); string s; List <double> numbers = new List <double>(); double x1 = 0, sum = 0, x2 = 0, x = 0, sum2 = 0; Math.Library.Math math = new Math.Library.Math(); while ((s = Console.ReadLine()) != null) { s = Regex.Replace(s, @"\s+", " "); string[] numbersString = s.Split(" "); foreach (var number in numbersString) { double n; bool success = Double.TryParse(number, out n); if (success) { numbers.Add(n); } else { Console.WriteLine("{0} is not valid number", number); return; } } } foreach (var n in numbers) { sum = math.Add(sum, n); } x1 = math.Add(math.Div(1, numbers.Count), sum); foreach (var n in numbers) { double n1 = 0, n2 = 0; n1 = math.Pow(n, 2); n2 = math.Mul(numbers.Count, math.Pow(x1, 2)); sum2 = math.Add(sum2, math.Sub(n1, n2)); } double res = math.Sqrt(math.Mul(math.Div(1, math.Sub(numbers.Count, 1)), x1), 2); Console.WriteLine(res); }