#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;
char in[28];
int search(int i){
	int result=0, count=0;
	//cout<<'r'<<i<<'l'<<i+d<<en;
	REP(j, 28){
		if((in[j]=='o')||(i<=j&&j<=i+d)){
			//cout<<(i<=j&&j<=i+d);
			count++;
			result=max(result, count);
		} else{
			count=0;
		}
	}
	//cout<<en;
	return result;
}
int main(){
	cin.tie();ios::sync_with_stdio(false);


	cin>>d;
	d--;
	fill_n(in,28,'x');
	FOR(i,7,21){
		cin>>in[i];
	}
	int result=0;
	REP(i, 28){
		result=max(result, search(i));
		//cout<<i<<' '<<result<<en;
	}
	cout<<result<<en;
	return 0;
}