using System.Collections.Generic;
using System;

public class Hello
{
    static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        var s = Console.ReadLine().Trim();
        getAns(n, s);
    }
    static void getAns(int n, string s)
    {
        var hs = new HashSet<string>();
        var t = s.ToCharArray();
        for (int i = 0; i < n - 1; i++)
        {
            var w = t[i];
            var w2 = t[i + 1];
            t[i] = 'B';
            t[i + 1] = 'B';
            hs.Add(new string(t));
            t[i] = w;
            t[i + 1] = w2;
        }
        Console.WriteLine(hs.Count);
    }
}