private void buttonSolveTask1_Click(object sender, EventArgs e)
{
int n = int.Parse(textBoxNTask1.Text);
library solver = new library();
double sum = solver.CalculateSum(n);
labelTask1Result.Text = "Сума дорівнює = " + sum.ToString();
}
static void Main(string[] args)
{
Console.Write("Введiть число: ");
int n = int.Parse(Console.ReadLine());
library solver = new library();
double sum = solver.CalculateSum(n);
Console.WriteLine("Сума довiвнює = " + sum);
}