using System;

using System.IO;

​

public class Program

{

    public static void Main()

    {

        Console.Clear();

        string[] CSV = new string[] {"9C:5C:8E:76:66:3F;201;1", "10:5C:8E:76:66:3F;202;2", "11:5C:8E:76:66:3F;203;3", "12:5C:8E:76:66:3F;204;4"};

        foreach(string line in CSV)

        {

            string[] splitLine = line.Split(';');

            string MAC = splitLine[0];

            string RNr = splitLine[1];

            string PCNr = splitLine[2];

            string IP = "10.16." + RNr + "." + PCNr;

            Console.WriteLine(MAC + ";" + IP + ";");

        }   

    }

}