07. Area of Figures

using System;

namespace Figures
{
    class Program
    {
        static void Main()
        {
            string figures = Console.ReadLine();
            double num1 = double.Parse(Console.ReadLine());
            double sum = 0;

            if (figures == "square")
            {
                sum = num1 * num1;
            }
            else if (figures == "rectangle")
            {
                double num2 = double.Parse(Console.ReadLine());
                sum = num1 * num2;
            }
            else if (figures == "circle")
            {
                sum = Math.PI * num1 * num1;
            }
            else if (figures == "triangle")
            {
                double num2 = double.Parse(Console.ReadLine());
                sum = num1 * num2 / 2;
            }
            Console.WriteLine($"{sum:f3}");
        }
    }
}