using System;

using System.Diagnostics;

​

public class Program

{

  public static string Format(double x, double y)

  {

      return String.Format("{0},{1}", x, y);

  }

  public static string Join(double x, double y)

  {

      return String.Join(",", x, y);

  }

  public static string Interpolate(double x, double y)

  {

      return $"{x},{y}";

  }

  public static string Sum(double x, double y) {

      return x + "," + y;

  }

​

  public static TimeSpan Time(Func<double, double, string> combine)

  {

      Stopwatch stopWatch = new Stopwatch();

      stopWatch.Start();

      for (int i = 0; i < 1500000; i++) {

          combine(3.14, 2.78);

      }

      stopWatch.Stop();

      return stopWatch.Elapsed;

  }

  public static void Main(string[] args)

  {

      Console.WriteLine(String.Format("Format:      {0}", Time(Format)));

      Console.WriteLine(String.Format("Join:        {0}", Time(Format)));

      Console.WriteLine(String.Format("Interpolate: {0}", Time(Format)));

      Console.WriteLine(String.Format("Sum:         {0}", Time(Format)));

  }

}