using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var tab = new [] { "KOT", "whatever", "KOT", "PIES" };

        ChangePiesToKot(tab);

        Console.WriteLine(!(tab.Any(x => x == "KOT")));

        Console.WriteLine(tab.Where(x => x == "PIES").Count() == 3);

    }

    private static void ChangePiesToKot(string[] values)

    {

        for (int i = 0; i < values.Length; i++)

        {

            if (values[i].Equals("KOT"))

                values[i] = "PIES";

        }

    }

}