using System;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        string[] arr = ["A", "B", "F", "D", "A", "B", "A", "G"];

        string str = String.Join(null, arr);

        int count = Regex.Matches(str, "AB").Count;

        Console.WriteLine(count);

    }

}