#include <bits/stdc++.h>

// debug
#ifdef LOCAL
#include <debug_print.hpp>
#define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#define debug(...) (static_cast<void>(0))
#endif

// #include "atcoder/all"

using namespace std;

using ll = long long;
using ld = long double;

void solve() {
    int N;
    string S;
    cin >> N >> S;

    bool no_change = false;

    int ans = 0;

    for (int i = 0; i < N - 1; i++) {
        if (S[i] == 'B' && S[i + 1] == 'B') {
            if (!no_change) {
                ans++;
                no_change = true;
            }
            continue;
        }
        if (S[i + 1] == 'A') {
            ans++;
            continue;
        }
        if (i == 0) {
            ans++;
            continue;
        }
        if (S[i - 1] == 'A') ans++;
    }

    cout << ans << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}