#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;
    rep(i,n-1){
        if(bx and s[i+1] == 'B') continue;
        bx = s[i] =='B';
        ans++;
    }
    cout << ans << endl;
    return 0;
}