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 int check2(int n, int[] t, int x, int y, int p)
    {
        var res = 0;
        for (int i = p; i < n - 1; i++)
        {
            for (int j = i + 1; j < n; j++)
            {
                if (t[i] == t[j]) continue;
                if (t[i] != x && t[i] != y && t[j] != x && t[j] != y) res++;
            }
        }
        return res;
    }
    static int check(int n, int[] t, int L, int r)
    {
        var res = 0;
        for (int i = L + 1; i < r; i++)
        {
            if (t[i] != t[L]) res += check2(n, t, t[L], t[i], r + 1);
        }
        return res;
    }
    static void getAns(int n, string s)
    {
        var t = new int[n];
        var aa = new List<int>[26];
        for (int i = 0; i < 26; i++) aa[i] = new List<int>();
        for (int i = 0; i < n; i++)
        {
            var w = s[i] - 'A';
            t[i] = w;
            aa[w].Add(i);
        }
        var ans = 0;
        for (int i = 0; i < 26; i++)
        {
            var aac = aa[i].Count;
            if (aac > 1)
            {
                for (int j = 0; j < aac - 1; j++)
                {
                    for (int k = j + 1; k < aac; k++)
                    {
                        ans += check(n, t, aa[i][j], aa[i][k]);
                    }
                }
            }
        }
        Console.WriteLine(ans);
    }
}