#include <iostream>
#include <vector>
#include <deque>
#include <stack>
#include <memory>
#include <functional>
#include <algorithm>
#include <map>
#include <list>
#include <complex>
#include <string>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <numeric>
#include <array>
using namespace std;
typedef std::pair<int, int> pii;
typedef long long int ll;

#define pb push_back

template < class BidirectionalIterator >
bool next_combination(BidirectionalIterator first1,
	BidirectionalIterator last1,
	BidirectionalIterator first2,
	BidirectionalIterator last2)
{
	if ((first1 == last1) || (first2 == last2)) {
		return false;
	}
	BidirectionalIterator m1 = last1;
	BidirectionalIterator m2 = last2; --m2;
	while (--m1 != first1 && !(*m1 < *m2)){
	}
	bool result = (m1 == first1) && !(*first1 < *m2);
	if (!result) {

		while (first2 != m2 && !(*m1 < *first2)) {
			++first2;
		}
		first1 = m1;
		std::iter_swap(first1, first2);
		++first1;
		++first2;
	}
	if ((first1 != last1) && (first2 != last2)) {

		m1 = last1; m2 = first2;
		while ((m1 != first1) && (m2 != last2)) {
			std::iter_swap(--m1, m2);
			++m2;
		}

		std::reverse(first1, m1);
		std::reverse(first1, last1);
		std::reverse(m2, last2);
		std::reverse(first2, last2);
	}
	return !result;
}

template < class BidirectionalIterator >
bool next_combination(BidirectionalIterator first,
	BidirectionalIterator middle,
	BidirectionalIterator last)
{
	return next_combination(first, middle, middle, last);
}

int main(){

	std::vector<char> data;
	std::vector<int> x;
	const int N = 14;

	int D;
	cin >> D;


	int result = 0;
	int count1 = 0;
	char c;

	int k = 0;
	for (k = 0; k < D; ++k) {
		data.pb('x');
		x.pb(k);
	}
	int j = k;
	for (j = k; j < N + D; ++j){
		cin >> c;
		data.push_back(c);
		if(c == 'o'){
			count1++;
		}else{
			count1 = 0;
		}
		result = max(result, count1);
		if(c == 'x'){
			x.pb(j);
		}
	}
	for (k = j; k < D + j; ++k) {
		data.pb('x');
		x.pb(k);
	}

	do{
		std::vector<char> tmp;
		for (int i = 0; i < data.size(); ++i) {
			tmp.pb(data[i]);
		}
		for (int i = 0; i < D; ++i) {
			tmp[x[i]] = 'o';
		}

		int count = 0;
		for (int i = 0; i < tmp.size(); ++i) {
			if(tmp[i] == 'o'){
				count++;
			}else{
				count = 0;
			}
			result = max(result, count);
		}
	} while (next_combination(x.begin(), x.begin() + D, x.end()));
	
	std::cout << result << std::endl;

	return 0;
}