#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;
//using mint = modint1000000007;
//using mint = modint998244353;



int main(){
  int N;
  cin >> N;
  string S;
  cin >> S;

  int ret = 0;
  map<int,int> m;
  int nochange = 0;
  rep(i,N-1){

    if(S[i] == 'A' && S[i+1] == 'A') ret++;
    else if(S[i] == 'A' && S[i+1] == 'B') m[i]++;
    else if(S[i] == 'B' && S[i+1] == 'A') m[i+1]++;
    else nochange++;
  }

  ret += m.size();
  if(nochange>0) ret++;
  
  cout << ret << endl;
  
  return 0;
}