#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;
  for(int i = 1; 14 > i; i++){
    if(s[i-1] != s[i]){
      A.push_back(t);
      t = 1;
    }else{
      t++;
    }
  }
  A.push_back(t);
  int ans = 0;
  A.push_back(0);
  for(int i = (s[0]=='o'); A.size()-1 > i; i+=2){
    if(!i){
      ans = min(n,A[i])+A[i+1];
    }else{
      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;
}