using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp6
{
    public partial class Lab1 : Form
    {
        public static bool Active;
        public Lab1()
        {
            InitializeComponent();
        }

        private void Lab1_Load(object sender, EventArgs e)
        {
            Active = true;
        }

        private void Lab1_FormClosed(object sender, FormClosedEventArgs e)
        {
            Active = false;
        }

        private void btnCalculate_Click(object sender, EventArgs ef)
        {
            try
            {
                MessageBox.Show($"Ответ: {Calculate(int.Parse(tbInputK.Text))}", "Ответ");
            } catch
            {
                MessageBox.Show($"Не верно заполнено поле", "Ошибка");
            }
        }
        static double Calculate(int num)
        {
            int k = num;
            double Sum = 0;
            double e = 0.001;
            while (true)
            {
                double term = Math.Pow(-1, k + 1) / (2 * k - 1);
                Sum += term;
                if (Math.Abs(term) < e)
                {
                    break;
                }
                k++;
            }
            double piOver4 = Sum;
            double pi = piOver4 * 4;
            double roundedpiOver4 = Math.Round(piOver4, 5);
            return roundedpiOver4;
        }
        public string MessagePull()
        {
            string message = $"Lab1 | Число K: {tbInputK.Text}";
            return message;
        }
    }
}