using System;

using System.Text.RegularExpressions;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var input = "  P.O, Box123;";

        var pattern = @"^ *|\.|,|;";

        var result = Regex.Replace(input, pattern, "");

        Console.WriteLine(result);

    }

}