Area of Circle in C#

The formula for finding the area of a circle is 3.14*r*r.

r- radius, 3.14 - Pi value

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

namespace ForgetCode
    class Program
        static void Main(string[] args)
            int r;
            double A;
            Console.WriteLine("Enter the radius:");
            r = Convert.ToInt32(Console.ReadLine());
            A = (3.14) * r * r;
            Console.WriteLine("The Area of circle of given radius is=" + A);