C#Basics_FiguresAreas

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

class Program
{
    static void Main()
    {
        string figure = Console.ReadLine().ToLower();
        double num1 = double.Parse(Console.ReadLine());

        if (figure == "rectangle")
        {
            double num2 = double.Parse(Console.ReadLine());
            Console.WriteLine(num1 * num2);
        }
        else if (figure == "triangle")
        {
            double num2 = double.Parse(Console.ReadLine());
            Console.WriteLine(num1 * num2 / 2);
        }
        else if (figure == "square")
        {
            Console.WriteLine(num1 * num1);
        }
        else if (figure == "circle")
        {
            Console.WriteLine(Math.PI * num1 * num1);
        }
    }

}