#include <iostream>
#include <algorithm>
#include <cmath>
#include <vector>
#include <complex>
#include <queue>
#include <set>
#include <map>

using namespace std;

#define REP(i,a,b) for(int i=a;i<(int)b;i++)
#define rep(i,n) REP(i,0,n)

typedef long long ll;

int main() {

  int D; cin >> D;
  char c[42];
  rep(i, 42) c[i] = 'x';
  REP(i, 14, 28) { cin >> c[i]; }

  int ans = 0;

  rep(i, 42) {

    int cnt1 = 0;
    for(int j=i-1; j>=0; j--) {
      if(c[j] == 'x') { break; }
      cnt1 ++;
    }

    int d = 0;
    REP(j, i, i+D) {
      if(c[j] == 'o') { break; }
      d++;
    }

    int cnt2 = 0;
    REP(j, i+d, 42) {
      if(c[j] == 'x') { break; }
      cnt2 ++;
    }
    ans = max(ans, cnt1 + cnt2 + d);
  }

  cout << ans << endl;

  return 0;
}