#include <iostream>
#include <string>
#include <vector>
using namespace std;

int main() {
    int n;
    cin >> n;
    string s;
    vector<int> idx;
    cin >> s;
    if (n == 1) {
        cout << 1 << endl;
        return 0;
    }
    int len = 1, maxlen = 0;
    bool change = false;
    for(int i=1;i<n;i++) {
        if (s[i] == s[i-1]) {
            len++;
            if(len>maxlen) maxlen = len;
            if (len == 2) {
                idx.push_back(i);
            }
        } else {
            change = true;
            len = 1;
        }
    }
    if(idx.size() >= 2)
        for(int i=idx[0];i<idx[1];i++)
            s[i] = 1 - (s[i] - '0') + '0';
    else if(idx.size() == 1)
        if (maxlen == 2)
            for(int i=idx[0];i<n;i++)
                s[i] = 1 - (s[i] - '0') + '0';
        else
            s[idx[0]] = 1 - (s[idx[0]] - '0') + '0';
    else if (!change) {
        s[1] = 1 - (s[1] - '0') + '0';
    }
    else
        for(int i=0;i<n;i++)
            s[i] = 1 - (s[i] - '0') + '0';
//    cout << s << endl;
    int ans = 1;
    for(int i=1;i<n;i++) {
        if (s[i] != s[i-1]) {
            ans++;
        }
    }
    cout << ans << endl;
}