import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.*;

public class Main {

    void solve() throws IOException {
        int n = ni();
        String t = "xxxxxxxxxxxxxx";
        String s = t + ns() + ns() + t;
        ArrayList<Integer> list = new ArrayList<>();
        int cnt = 1;
        for (int i = 0; i < s.length() - 1; i++) {
            if (s.charAt(i) == s.charAt(i + 1)) {
                cnt++;
            } else {
                list.add(cnt);
                cnt = 1;
            }
        }
        list.add(cnt);

        int ans = 0;
        for (int i = 1; i < list.size(); i += 2) {
            if (list.get(i - 1) >= n || list.get(i + 1) >= n) {
                ans = Math.max(ans, list.get(i) + n);
            }
            if (i != 1 && list.get(i - 1) <= n) {
                ans = Math.max(ans, list.get(i - 2) + list.get(i - 1) + list.get(i));
            }
        }

        out.println(ans);
    }

    String ns() throws IOException {
        while (!tok.hasMoreTokens()) {
            tok = new StringTokenizer(in.readLine(), " ");
        }
        return tok.nextToken();
    }

    int ni() throws IOException {
        return Integer.parseInt(ns());
    }

    long nl() throws IOException {
        return Long.parseLong(ns());
    }

    double nd() throws IOException {
        return Double.parseDouble(ns());
    }

    String[] nsa(int n) throws IOException {
        String[] res = new String[n];
        for (int i = 0; i < n; i++) {
            res[i] = ns();
        }
        return res;
    }

    int[] nia(int n) throws IOException {
        int[] res = new int[n];
        for (int i = 0; i < n; i++) {
            res[i] = ni();
        }
        return res;
    }

    long[] nla(int n) throws IOException {
        long[] res = new long[n];
        for (int i = 0; i < n; i++) {
            res[i] = nl();
        }
        return res;
    }

    static BufferedReader in;
    static PrintWriter out;
    static StringTokenizer tok;

    public static void main(String[] args) throws IOException {
        in = new BufferedReader(new InputStreamReader(System.in));
        out = new PrintWriter(System.out);
        tok = new StringTokenizer("");
        Main main = new Main();
        main.solve();
        out.close();
    }
}