#include <string>
#include <vector>
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<stack>
#include<queue>
#include<cmath>
#include<algorithm>
#include<functional>
#include<list>
#include<deque>
#include<bitset>
#include<set>
#include<map>
#include<unordered_map>
#include<unordered_set>
#include<cstring>
#include<sstream>
#include<complex>
#include<iomanip>
#include<numeric>
#include<cassert>
#define X first
#define Y second
#define pb push_back
#define rep(X,Y) for (int (X) = 0;(X) < (Y);++(X))
#define reps(X,S,Y) for (int (X) = S;(X) < (Y);++(X))
#define rrep(X,Y) for (int (X) = (Y)-1;(X) >=0;--(X))
#define repe(X,Y) for ((X) = 0;(X) < (Y);++(X))
#define peat(X,Y) for (;(X) < (Y);++(X))
#define all(X) (X).begin(),(X).end()
#define rall(X) (X).rbegin(),(X).rend()
#define eb emplace_back
#define UNIQUE(X) (X).erase(unique(all(X)),(X).end())
#define Endl endl

using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<class T> using vv=vector<vector<T>>;
template<class T> ostream& operator<<(ostream &os, const vector<T> &t) {
os<<"{"; rep(i,t.size()) {os<<t[i]<<",";} os<<"}"<<endl; return os;}
template<class S, class T> ostream& operator<<(ostream &os, const pair<S,T> &t) { return os<<"("<<t.first<<","<<t.second<<")";}
template<class T> inline bool MX(T &l,const T &r){return l<r?l=r,1:0;}
template<class T> inline bool MN(T &l,const T &r){return l>r?l=r,1:0;}
#define out(args...){vector<string> a_r_g_s=s_p_l_i_t(#args, ','); e_r_r(a_r_g_s.begin(), args); }
vector<string> s_p_l_i_t(const string& s, char c) { vector<string> v; stringstream ss(s); string x; while(getline(ss,x,c)) v.emplace_back(x); return move(v);}
void e_r_r(vector<string>::iterator it) {}
template<typename T, typename... Args> void e_r_r(vector<string>::iterator it, T a, Args... args){ if(*it==" 1"||*it=="1") cerr<<endl; else cerr << it -> substr((*it)[0] == ' ', it -> length()) << " = " << a << ", "; e_r_r(++it, args...);}
const ll MOD=1e9+7;
int orig[555][555];
int main(){
  ios_base::sync_with_stdio(false);
  cout<<fixed<<setprecision(0);
  int n;
  cin>>n;
  rep(i,n){
    string s;
    cin>>s;
    rep(j,n) orig[i][j]=(s[j]=='#');
  }
  if(accumulate(orig[0],orig[555],0)==0){
    cout<<-1<<endl;
    return 0;
  }
  int cnt=0;
  vector<int> ex(n);
  rep(x,n){
    int f=1;
    rep(y,n){
      if(orig[y][x]==0) f=0;
      else ex[x]=1;
    }
    if(!f) ++cnt;
  }
  if(!cnt){
    cout<<0<<endl;
    return 0;
  }
  int re=MOD;
  rep(t,n){
    int sum=0;
    int bs=accumulate(orig[t],orig[t]+n,0);
    if(bs<n){
      if(ex[t]) sum+=n-bs;
      else sum+=n-bs+1;
    }
    MN(re,sum+cnt);
  }
  cout<<(re==MOD?-1:re)<<endl;
  // queue<AR> que; que.push(orig);
  // map<AR,int> dst; dst[orig]=0;
  // while(que.size()){
  //   AR t=que.front(); que.pop();
  //   int f=1;
  //   rep(i,n)rep(j,n)if(t[i][j]==0) f=0;
  //   if(f){
  //     cout<<dst[t]<<endl;
  //     return 0;
  //   }
  //   rep(i,n)rep(j,n){
  //     AR nxt=t;
  //     rep(k,n) nxt[k][j]=t[i][k];
  //     if(dst.count(nxt)) continue;
  //     dst[nxt]=dst[t]+1;
  //     que.push(nxt);
  //   }
  // }
  // cout<<-1<<endl;
  return 0;
}


Measured memory_bytes: 1408