#include <bits/stdc++.h>
using namespace std;
char s[100005];
int main() {
  int n;
  while (cin >> n) {
    scanf("%s", s);
    int ct = 1, n = strlen(s);
    bool ok = false;
    int cant = 0, ans = 0;
    for (int i = 1; i < n; i++) {
      if (s[i] == s[i - 1])
        ct++;
      else {
        if (ct >= 3) ok = true;
        if (ct >= 2) cant++;
        ans++;
        ct = 1;
      }
    }
    ans++;
    if (ct >= 3) ok = true;
    if (ct >= 2) cant++;
    if (ok)
      ans += 2;
    else {
      if (cant >= 2)
        ans += 2;
      else if (cant == 1)
        ans++;
    }
    cout << ans << endl;
  }
}
