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

int main() {
    int N;
    string S;
    cin >> N >> S;
    int ans = 0,f = 0;
    for(int i = 0; i+1 < N; i++) {
        if(S[i] == 'B' && S[i+1] == 'B') {
            f = 1;
            continue;
        }
        else if(i && S[i-1] == 'B' && S[i+1] == 'B') {
            continue;
        }
        else {
            ans++;
        }
    }
    cout << ans+f << endl;
}