// includes
#include <bits/stdc++.h>
using namespace std;

// macros
#define pb emplace_back
#define mk make_pair
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define irep(itr, st) for(auto itr = (st).begin(); itr != (st).end(); ++itr)
#define irrep(itr, st) for(auto itr = (st).rbegin(); itr != (st).rend(); ++itr)
#define whole(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define bit(n) (1LL<<(n))
// functions
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}
template <typename T> ostream &operator<<(ostream &os, const vector<T>& vec){for(int i = 0; i < vec.size(); i++){ os << vec[i]; if(i + 1 != vec.size())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T>& st){for(auto itr = st.begin(); itr != st.end(); ++itr){ os << *itr; auto titr = itr; if(++titr != st.end())os << " ";} return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){os << "(" << p.first << ", " << p.second << ")"; return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
template <typename T1, typename T2> ostream &operator<<(ostream &os, const unordered_map<T1, T2> &mp){for(auto itr = mp.begin(); itr != mp.end(); ++itr){ os << "(" << itr->first << ", " << itr->second << ")"; auto titr = itr; if(++titr != mp.end())os << " "; } return os;}
//  types
using ll = long long int;
using P = pair<int, int>;
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1000000007;
const int dx[4] = {-1, 0, 1, 0};
const int dy[4] = {0, -1, 0, 1};
// io
struct fast_io{
  fast_io(){ios_base::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(20);}
} fast_io_;

string s[501];
int dp[501][501];
bool used[501][501];
int cnt[501];

int main(int argc, char const* argv[])
{
  int n; cin >> n;
  rep(i, n)cin >> s[i];
  bool ok = false;
  rep(i, n){
    rep(j, n){
      if(s[i][j] == '#')ok = true;
    }
  }
  if(!ok){
    cout << -1 << endl;
    return 0;
  }

  rep(i, n){
    rep(j, n){
      if(s[i][j] == '#'){
        cnt[j]++;
      }
    }
  }

  queue<P> q;
  rep(i, n){
    rep(j, n){
      if(s[i][j] == '#'){
        used[i][j] = true;
        q.push(mk(i, j));
      }
    }
  }
  while(!q.empty()){
    int x, y; tie(x, y) = q.front(); q.pop();
    rep(z, n){
      if(!used[y][z]){
        used[y][z] = true;
        dp[y][z] = dp[x][y] + 1;
        q.push(mk(y, z));
      }
    }
  }
  /*
  rep(i, n){
    rep(j, n){
      cerr << dp[i][j] << "\n "[j + 1 != n];
    }
  }
  /*/

  int res = inf;
  rep(i, n){
    int mini = inf, idx = -1;
    rep(j, n){
      if(mini > dp[j][i]){
        mini = dp[j][i];
        idx = j;
      }
    }
    int tmp = mini;
    rep(j, n){
      if(s[i][j] == '.')++tmp;
    }
    rep(j, n){
      if(cnt[j] != n)++tmp;
    }
    chmin(res, tmp);
  }
  cout << res << endl;
  return 0;
}


Measured memory_bytes: 3840