Area of Figures

using System;

class Program
{
    static void Main()
    {
        string figure = Console.ReadLine();

        if (figure == "square")
        {
            var numOne = double.Parse(Console.ReadLine());
            var square = Math.Round(numOne * numOne, 3);
            Console.WriteLine(square);
        }
        else if (figure == "rectangle")
        {
            var numOne = double.Parse(Console.ReadLine());
            var numTwo = double.Parse(Console.ReadLine());
            var rectangle = Math.Round(numOne * numTwo, 3);
            Console.WriteLine(rectangle);
        }
        else if (figure == "circle")
        {
            var numOne = double.Parse(Console.ReadLine());
            var circle = Math.Round(Math.PI * numOne * numOne, 3);
            Console.WriteLine(circle);
        }
        else if (figure == "triangle")
        {
            var numOne = double.Parse(Console.ReadLine());
            var numTwo = double.Parse(Console.ReadLine());
            var triangle = Math.Round(numOne * numTwo / 2, 3);
            Console.WriteLine(triangle);
        }
    }
}