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

struct Holiday {
	Holiday(int days, int start) {
		this->days = days;
		this->start = start;
	}
	int days;
	int start;
};

int main() {
	const int NUM_OF_DAYS = 14;

	int d;
	cin >> d;

	char calendar[NUM_OF_DAYS + 1];
	
	int index = 0;
	char buf[8];
	for (int i = 0; i < 2; i++) {
		cin >> buf;
		for (int j = 0; j < 7; j++) {
			calendar[index++] = buf[j];
		}
	}
	calendar[NUM_OF_DAYS] = '\0';

	vector<Holiday> holidays;
	index = 0;
	while (index < NUM_OF_DAYS) {
		while (calendar[index] == 'x')
			index++;

		if (calendar[index] == '\0')
			break;

		int startIndex = index;
		while (calendar[index] == 'o')
			index++;

		holidays.push_back(Holiday(index - startIndex, startIndex));
	}

	int maxDays = 0;
	if (holidays.size() == 0) {
		maxDays = d;
	}
	else {
		for (int i = 0; i < holidays.size(); i++) {
			if (i == 0) {
				maxDays = max(maxDays, holidays[i].days + d);
			}
			else {
				Holiday prev = holidays[i - 1];
				Holiday current = holidays[i];
				int interval = current.start - (prev.start + prev.days);
				if (d < interval)
				{
					maxDays = max(maxDays, prev.days + d);
					maxDays = max(maxDays, current.days + d);
				}
				else {
					maxDays = max(maxDays, prev.days + interval + current.days);
				}

				if (i == holidays.size() - 1)
					maxDays = max(maxDays, current.days + d);
			}
		}
	}

	cout << maxDays << endl;

	return 0;
}