import java.util.Scanner;

public class Main {
    public static void main(String[] argv) {
        Scanner scanner = new Scanner(System.in);
        int d = scanner.nextInt();
        String s = scanner.next();
        s += scanner.next();
        int res = 0;
        for (int i = 0; i < 14 - d + 1; ++i) {
            boolean ok = true;
            for (int j = 0; j < d; ++j) {
                if (s.charAt(i + j) == 'o') {
                    ok = false;
                    break;
                }
            }
            int count = 0;
            for (int j = 0; j < 14; ++j) {
                boolean isYukyu = ok && (j - i >= 0) && ((j - i) < d);
                if (s.charAt(j) == 'o' || isYukyu) {
                    count++;
                    res = Math.max(res, count);
                } else {
                    count = 0;
                }
            }
        }
        System.out.println(res);
    }
}