using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string str="zaeazeaze2018azeazeazeazeaze2018azezaazeazeaze4azeaze2018";

        string regexPattern = @"2018";

        int numberOfOccurence = Regex.Matches(str, regexPattern).Count;

        Console.WriteLine(numberOfOccurence);

    }

}