#include <bits/stdc++.h>
#include<iostream>
#include<map>
#include<vector>
#include <algorithm>
#include<math.h>
#include <iomanip>
#include<set>
#include <numeric>
#include<string>
using ll = long long;
using namespace std;

int main()
{
    ll n;
    string s, tmp;
    cin >> n >> s;
    set<string> st;
    for (int i = 0; i < n-1; i++){
        tmp = s;
        if (tmp[i] == 'A') tmp[i] = 'B';
        if (tmp[i+1] == 'A') tmp[i+1] = 'B';
        st.insert(tmp);
    }
    cout << st.size() << endl;
}