#include<iostream>
#include<string>

#define ll long long
#define rep(i,s,t) for(int i = s; i < t; i++)

using namespace std;

int N = 0;
int ans = 0;
string src = "";

bool jud(char c,int skp_ind,string s)
{
    rep(i,0,s.size())
    {
        if(i == skp_ind)continue;
        if(c == s[i])return false;
    }

    return true;
}

void rec(int ind,string s)
{
    if(s.size() == 5)
    {

        if(s[0] == s[2] && jud(s[1],1,s) && jud(s[3],3,s) && jud(s[4],4,s))
        {
            ans++;
            return;
        }
        else return;
    }

    rep(i,ind+1,N)
    {
        string piyo = "";
        piyo += src[i];
        rec(i,piyo);
    }

    return;
}

int main()
{
    cin >> N >> src;

    rep(i,0,N)
    {
        string piyo = "";
        piyo += src[i];
        rec(i,piyo);
    }

    cout << ans << endl;

    return 0;
}