#include "bits/stdc++.h"
using namespace std;

#define FOR(i,s,g) for(int i=s;i<g;i++)
#define REP(i,  n) for(int i=0;i<n;i++)

using ull = unsigned long long;
using  ll =          long long;

const char en = '\n';
const ull  INFL = 810000001919114514;
const ull  INF  =         1919114514;


int d;
using D = vector<int>;

D in;
int main(){
	cin.tie();ios::sync_with_stdio(false);
	
	cin>>d;

	char curc='x',buf;
	int curv=114514;
	REP(i,14){
		cin>>buf;
		if(buf==curc){
			curv++;
		}else{
			curc=buf;
			in.push_back(curv);
			curv=1;
		}
	}
	if(curc=='x'){
		in.push_back(curv+114514);
	}else{
		in.push_back(curv);
		in.push_back(114514);
	}


	in.push_back(0);

	/*
		for(int i=0;i<in.size();i++){
			cout<<in[i]<<' ';
		}
		cout<<en;
	*/

	int result=d+in[1];
	for(int i=2;i<in.size()-1;i+=2){
		if(in[i]<=d){
			result=max(result,in[i-1]+in[i]+in[i+1]);
		}else{
			result=max(result, in[i-1]+d);
			result=max(result, in[i+1]+d);
		}
	}

	cout<<result<<en;

	return 0;
}