#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0;i<n;i++)
#define all(x) x.begin(),x.end() 
#define yesif(x) cout << ((x) ? "Yes": "No") << endl
#define myceil(a, b) (a+b-1)/b 
using namespace std;
typedef long long ll;

int main() {
    int n; cin >> n;
    string s; cin >> s;
    int ans = 0;
    bool bx = false;
    bool bb = false;
    rep(i,n-1){
        string t = s;
        if(bx and s[i+1] == 'B') {
            bx = s[i] =='B';
            continue;
        }
        bx = s[i] =='B';
        if(s[i] == 'B' and s[i+1] == 'B') {
            bb = true;
            continue;
        }
        ans++;

    }
    if(bb) ans++;
    cout << ans << endl;
    return 0;
}