#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (ll i = 0; i < n; ++ i)
#define all(x) (x).begin(),(x).end()
using ll = long long ;
using P = pair<ll,ll>;
using PP = pair<ll,P>;
using vi = vector<ll>;
using vb = vector<bool>;
using vp = vector<P>;
using vii = vector<vi>;
const ll INF = (1<<30);
const int inf = 1001001001;
const int dx[4]={1,-1,0,0};
const int dy[4]={0,0,1,-1};
const ll mod=998244353;
int main(){
    int n;
    string s;
    cin >> n >> s;
    int nn = n-1;
    bool K = false;
    rep(i,n-1){
        if(s[i] == s[i+1] && s[i] =='B') {--nn; K =true;}
        if(i+2 != n && s[i] == s[i+2] && s[i] =='B') --nn;
    }   
    if(K) ++nn;
    cout<<nn<<endl;
}