#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}


template<typename T>
vector<T> compress(vector<T> v){
  sort(v.begin(),v.end());
  v.erase(unique(v.begin(),v.end()),v.end());
  return v;
}

template<typename T>
map<T, Int> dict(const vector<T> &v){
  map<T, Int> res;
  for(Int i=0;i<(Int)v.size();i++)
    res[v[i]]=i;
  return res;
}

//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  vector<string> s(n);
  for(Int i=0;i<n;i++) cin>>s[i];
  
  Int ans=n+1;
  vector<Int> cnt(n,0);
  function<void(Int, Int)> dfs=
    [&](Int y,Int x){
      if(y==n){
        chmin(ans,n-dict(compress(cnt))[cnt[0]]);
        return;
      }
      Int nx=(x+1)%n,ny=y+!nx;
      if(x<=y) dfs(ny,nx);
      if(s[y][x]!='x'){
        cnt[y]++;
        dfs(ny,nx);
        cnt[y]--;
      }
      if(s[y][x]!='o'){
        cnt[x]++;
        dfs(ny,nx);
        cnt[x]--;
      }
    };
  dfs(0,0);
  cout<<ans<<endl;
  return 0;
}