#include <bits/stdc++.h>
using namespace std;

static inline void solution() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  set<string> st;
  for (int i = 0; i < n - 1; i++) {
    char a = s[i], b = s[i + 1];
    s[i] = 'B', s[i + 1] = 'B';
    st.insert(s);
    s[i] = a, s[i + 1] = b;
  }
  cout << st.size() << '\n';
}

int main() {
  ios_base::sync_with_stdio(0), cin.tie(0);
  solution();
  return 0;
}