#include<iostream>
#include<cstdio>
#include<cstring>
#include <cstdlib>  
#include <cmath>   
#include<cctype>
#include<string>
#include<set>
#include<iomanip>
#include <map>
#include<algorithm>
#include <functional>
#include<vector>
#include<climits>
#include<stack>
#include<queue>
#include <deque>
#include <climits>
#include <typeinfo>
#include <utility> 
#define all(x) (x).begin(),(x).end()
#define rep(i,m,n) for(int i = m;i < n;++i)
#define pb push_back
#define fore(i,a) for(auto &i:a)
#define rrep(i,m,n) for(int i = m;i >= n;--i)
#define INF INT_MAX/2
using namespace std;
using ll = long long;
using R = double;
using Data = pair<ll, vector<int>>;
const ll MOD = 1e9 + 7;
const ll inf = 1LL << 50;
struct edge { ll from; ll to; ll cost; };




int main() {
	int d;
	cin >> d;
	string date = "";
	rep(i, 0, 2) {
		string s;
		cin >> s;
		date += s;
	}

	int ans = -101010;
	rep(i, 0, 14) {
		if (date[i] == 'x') {
			string temp = date;
			int cnt = 0;
			rep(j, i, 14) {
				if (date[j] == 'o' || cnt == d)break;
				cnt++;
				temp[j] = 'o';
			}

			int seq = 0;
			rep(k, 0, 14) {
				if (temp[k] == 'o')seq++;
				else seq = 0;
				ans = max(seq, ans);
			}
		}
	}
	cout << ans << endl;

	return 0;
}