public class Program
{
    public static void Main()
    {
        int num = int.Parse(Console.ReadLine() ?? string.Empty);
        int num2 = int.Parse(Console.ReadLine() ?? string.Empty);
        string[] str = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');

        List<string> list = [];
        AB(num, list, "",str);

       Console.WriteLine(list.Count);
    }

    static void AB(int length, List<string> list, string str, string[] moji)
    {
        if (str.Length == length)
        {
            for (int i = 0; i < moji.Length; i++)
            {
                if(str.LastIndexOf(moji[i]) == length-3)
                {
                    list.Add(str);
                }
            }
            return;
        }
        char[] ab = ['A', 'B'];
        string dna = str;
        for (int i = 0; i < ab.Length; i++)
        {
            AB(length, list, dna + ab[i],moji);
        }
    }
}