#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
  int N;
  string S,T;
  cin>>N>>S>>T;
  S += T;
  T = S;
  int ans = 0;
  for(int z=0;z<14-N;z++){
      for(int y=z;y<z+N;y++) S[y] = 'o';
  int now = 0;
  for(int i=0;i<14;i++){
      if(S[i] == 'o') now++;
      else now = 0;
      ans = max(ans,now);
  }
  S = T;
  }
  cout<<ans<<endl;
}