#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, cnt = 1;
  string s;
  cin >> n >> s;
  for (int i = 0; i < n - 1; i++) {
    if (s[i] != s[i + 1]) {
      cnt++;
    }
  }
  cout << min(cnt + 2, n);
  return 0;
}
