Math.Abs

   
  
using System;

public class MainClass {
    public static void Main() {

        Console.WriteLine("Math.Abs(5) = {0}", Math.Abs(5));
        Console.WriteLine("Math.Abs(-5) = {0}", Math.Abs(-5));
        Console.WriteLine("Math.Abs(0) = {0}", Math.Abs(0));
    }
}