#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <fstream>
#include <sstream>
#include<set>
#include<stack>
#include<time.h>
#include <sys/types.h>
#include <tuple>
#include <numeric>
#include <iterator>

typedef long long int ll;
//#include<bits/stdc++.h>


using namespace std;

ll gcd(ll a, ll b) {
    if (a < b)swap(a, b);
    if (b == 0)return a;
    return gcd(b, a % b);
}
int lcm(int a, int b) {
    return a * b / gcd(a, b);
}

long long mod_exp(long long b, long long e, long long m) {
    if (e > 0 && b == 0) return 0;
    long long ans = 1;
    b %= m;

    while (e > 0) {
        if ((e & 1LL)) ans = (ans * b) % m;
        e = e >> 1LL;
        b = (b * b) % m;
    }

    return ans;
}


int main()
{

    int Q;
    Q = 1;
    //cin >> Q;



    while (Q--) {
        int d  ; cin >> d;
        string p;
        cin >> p;
        if (p.size() < 5)cout << 0;
        else {
            vector<int>a(d);
            for (int i = 0; i < p.size(); i++) {
                a[i] = i;
            }
            ll ans = 0;
            int n = a.size();
            for (int i0 = 0; i0 < d; i0++) {
                string x;
                
                for (int i1 = i0+1; i1 < d; i1++) {
                    for (int i2 = i1+1; i2 < d; i2++) {
                        for (int i3 = i2+1; i3 < d; i3++) {
                            for (int i4 = i3+1; i4 < d; i4++) {
                                if (p[i0] == p[i2]) {
                                    set<char>s;
                                    s.insert(p[i0]); s.insert(p[i1]);
                                    s.insert(p[i2]); s.insert(p[i3]);
                                    s.insert(p[i4]); 
                                    if (s.size() == 4)ans++;
                                }

                            }

                        }

                    }

                }

            }

            cout << ans;
        }

    }
        return 0;
    }