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

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';

	int maxDays = 0;
	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++;

		int paidDays = d;
		while (paidDays > 0 && calendar[index] == 'x') {
			index++;
			paidDays--;
		}

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

		if (index < NUM_OF_DAYS) {
			while (calendar[index] == 'o')
				index++;
		}
		
		maxDays = max(maxDays, index - startIndex);
	}

	cout << maxDays << endl;

	return 0;
}