#include <iostream>
#include <vector>
using namespace std;
int main(){
  int n;cin>>n;
  string s,b;cin>>s>>b;
  s+=b;
  vector<int> A;
  int t = 1;
  int ans = 0;
  if(s[0] == 'o')A.push_back(14);
  else t+=14;
  for(int i = 1; 14 > i; i++){
    if(s[i-1] != s[i]){
      if(s[i-1] == 'o')ans = max(ans,t);
      A.push_back(t);
      t = 1;
    }else t++;
  }
  if(s[13] == 'o'){
    A.push_back(t);
    A.push_back(14);
  }
  else{
    A.push_back(t+14);
  }
  for(int i = (s[0]=='x'); A.size()-1 > i; i+=2){
    if(A[i] > n){
      ans = max(ans,max(n+A[i-1],n+A[i+1]));
    }else{
      ans = max(ans,A[i-1]+A[i+1]+A[i]);
    }
  }
  cout << ans << endl;
}