Area of figures

Area of figures

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Numerics;
using System.Globalization;
using System.Text.RegularExpressions;

namespace Praktice
{
    class Program
    {
        static void Main(string[] args)
        {
            string word = (Console.ReadLine());
            if (word == "square")
            {
                var a = double.Parse(Console.ReadLine());
                var area = a * a;
                Console.WriteLine(area);
            }
 
            if (word == "rectangle")
            {
                var x = double.Parse(Console.ReadLine());
                var y = double.Parse(Console.ReadLine());
                var area1 = x * y;
                Console.WriteLine(area1);
            }
            if (word == "circle")
            {
                var r = double.Parse(Console.ReadLine());
                Console.WriteLine("Area = " + Math.PI * r * r);
            }
            if (word == "triangle")
            {
                var a = double.Parse(Console.ReadLine());
                var h = double.Parse(Console.ReadLine());
                var area2 = a * h / 2;
                Console.WriteLine(Math.Round(area2, 2));
            }
        }
    }
}