for the area of a circle in C#

Question

ever time i run this code it gives me an error in the code coach

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

namespace SoloLearn
{
class Program
{
static void Main(string[] args)
{
double pi = 3.14;
int radius = Convert.ToInt32(Console.ReadLine());

Console.WriteLine((radius * radius) * pi);

}
}
}