#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <algorithm>
#include <stack>
#include <atcoder/all>
using namespace std;

#define reps(i, a, n) for (int i = (a); i < (int)(n); ++i)
#define rep(i, n) reps(i, 0, n)

#define ALL(x) x.begin(),x.end() 
#define SIZE(x) ll(x.size()) 

#define INF32 2147483647 //2.147483647×10^{9}:32bit整数のinf
#define INF64 9223372036854775807 //9.223372036854775807×10^{18}:64bit整数のinf
#define MOD 1000000007 //問題による

#define ll long long


#define F first
#define S second

#define coutALL(x) for(auto i=x.begin();i!=--x.end();i++)cout<<*i<<" ";cout<<*--x.end()<<endl;
#define coutALL2d(vv) for(const auto& v : vv){for(const auto& e : v){cout << e << " ";}cout << endl;}

#define vi vector<int>
#define vvi vector<vector<int> >
#define vll vector<long long>
#define vvll vector<vector<long long> >

int main(){
    int n;
    cin >> n;
    string s;
    cin >> s;
    int cnta = 0;
    int cntb = 0;

    int res = 0;
    reps(i,1,n){
        if(s[i-1] == 'B' && s[i] == 'A' && cnta == 1){
            res += (cntb + 1);
            cnta = 1;
            cntb = 0;
        }
        else if(s[i-1] == 'B' && s[i] == 'A' && cnta == 0){
            cnta = 1;
        }
        else if(s[i-1] == 'B'&& s[i] == 'B'){
            cntb++;
        }
        else if(s[i-1] == 'A' && s[i] == 'A'){
           cnta = 0;
           cntb = 0; 
        }
        //cout << cnta << " " << cntb << " " <<res <<endl;
    }
    cout << n-1-res << endl;

}