#include <bits/stdc++.h>
using namespace std;
int inf_int = 2e9;
long long inf_ll = 2e18;
const double pi = 3.1415926535898;
template <typename T>
void prin(vector<T>& a) {
  for (int i = 0; i < a.size(); i++) {
    cout << a[i] << " ";
  }
}
template <typename T>
void prin_new_line(vector<T>& a) {
  for (int i = 0; i < a.size(); i++) {
    cout << a[i] << "\n";
  }
}
int sum_vec(vector<int>& a) {
  int s = 0;
  for (int i = 0; i < a.size(); i++) {
    s += a[i];
  }
  return s;
}
template <typename T>
T max(vector<T>& a) {
  T ans = a[0];
  for (int i = 1; i < a.size(); i++) {
    ans = max(ans, a[i]);
  }
  return ans;
}
template <typename T>
T min(vector<T>& a) {
  T ans = a[0];
  for (int i = 1; i < a.size(); i++) {
    ans = min(ans, a[i]);
  }
  return ans;
}
int min(int a, int b, int c) { return min(a, min(b, c)); }
long long min(long long a, long long b, long long c) {
  return min(a, min(b, c));
}
int max(int a, int b, int c) { return max(a, max(b, c)); }
long long max(long long a, long long b, long long c) {
  return max(a, max(b, c));
}
double s_triangle(double x1, double y1, double x2, double y2, double x3,
                  double y3) {
  return (((x2 - x1) * (y3 - y1) - (x3 - x1) * (y2 - y1)) / 2);
}
void solve() {
  int n;
  cin >> n;
  string a;
  cin >> a;
  int ans = 1;
  for (int i = 1; i < n; i++) {
    if (a[i] != a[i - 1]) ans++;
  }
  cout << min(ans + 2, n);
}
int main() {
  if (!0) {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
  }
  int t = 1;
  while (t--) solve();
}
