#include<iostream>
#include<string>
#include<algorithm>

int main() {
	int holiday;
	std::string weeks, s;

	std::cin >> holiday;
	std::cin >> s;
	weeks = s;
	std::cin >> s;
	weeks += s;

	int max = holiday;
	//ゴールデンウィークの前から有給をとる場合
	for (int i = 0; weeks[i] == 'o'; i++) {
		max++;
	}

	for (int i = 0; i < weeks.length(); i++) {
		int count = 0, holi_num = 0;
		bool flag = false;
		int j = i;
		while (j < weeks.length() && weeks[j] == 'o') {
			holi_num++;
			j++;
		}
		while (j < weeks.length() && weeks[j] == 'x' && count != holiday) {
			count++;
			holi_num++;
			j++;
		}
		while (j < weeks.length() && weeks[j] == 'o') {
			flag = true;
			holi_num++;
			j++;
		}
		if (!flag)holi_num += holiday - count;
		max = std::max(max, holi_num);
	}

	std::cout << max << std::endl;
	return 0;
}