Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args);
        
            class Calculator
    {
        private Double _num1;
        private Double _num2;

        public Double PI
        {
            get
            {
                return Math.PI;
            }
        }

        public Calculator(Double num1, Double num2)
        {
            this._num1 = num1;
            this._num2 = num2;
        }

        public void WriteNumber1()
        {
            Console.WriteLine(this._num1);
        }

        public void WriteNumber2()
        {
            Console.WriteLine(this._num2);
        }

        public Double Add()
        {
            return this._num1 + this._num2;
        }

        public Double Subtract()
        {
            return this._num1 - this._num2;
        }

        public Double Multiply()
        {
            return this._num1 * this._num2;
        }

        public Double Divide()
        {
            return this._num1 / this._num2;
        }

        public static Double Add(Double num1,Double num2)
        {
            return num1 + num2;
        }

        public static Double Subtract(Double num1, Double num2)
        {
            return num1 - num2;
        }

        public static Double Multiply(Double num1, Double num2)
        {
            return num1 * num2;
        }

        public static Double Divide(Double num1, Double num2)
        {
            return num1 / num2;
        }

        public static Double PovrsinaKruga(Double poluprecnik)
        {
            return Math.PI * 2 * poluprecnik;
        }
    }
        }
    }