#define _USE_MATH_DEFINES
#include<stdio.h>
#include<string>
#include<iostream>
#include<cctype>
#include<cstdio>
#include<vector>
#include<stack>
#include<queue>
#include <algorithm>
#include<math.h>
#include<set>
#include<map>
#include<iomanip>

//#include<bits/stdc++.h>


using namespace std;


int main() {
	
	int n; cin >> n;
	string a, b;
	cin >> a >> b;
	string g = a + b;
	int s = 0;
	for (int i = 0; i < g.size(); i++) {
		int x = 0;
		string p = g;
		for (int j = i; j < g.size(); j++) {
			if (p[j] == 'x') {
				p[j] = 'o';
				x++;
			}
			if (x >= n)break;
		}
		int y = 0;
		for (int j = 0; j < p.size(); j++) {
			if (p[j] == 'o')y++;
			else y = 0;
			s = max(s, y);
		}

		


	}
	cout << s << endl;

	return 0;


}