using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Input x = ");

        var x = double.Parse(Console.ReadLine());

        double y ;

        if ( x<1 )

        {

            Console.Write("y = ");

            Console.WriteLine(y=x+1);

            }

        else

            if( x>=1 && x<=3 )

        {

            Console.WriteLine("y=");

            Console.WriteLine("y=3*x-3");

         }

        else

        Console.Write("y=");

        Console.WriteLine(y=2*x);

       }

    }

​