#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ull = unsigned long long;
 
#define ALL(obj) (obj).begin(),(obj).end()
#define SPEED cin.tie(0);ios::sync_with_stdio(false);
 
template<class T> using PQ = priority_queue<T>;
template<class T> using PQR = priority_queue<T,vector<T>,greater<T>>;
 
constexpr long long MOD = (long long)1e9 + 7;
constexpr long long MOD2 = 998244353;
constexpr long long HIGHINF = (long long)1e18;
constexpr long long LOWINF = (long long)1e15;
constexpr long double PI = 3.1415926535897932384626433;
 
template <class T> vector<T> multivector(size_t N,T init){return vector<T>(N,init);}
template <class... T> auto multivector(size_t N,T... t){return vector<decltype(multivector(t...))>(N,multivector(t...));}
template <class T> void corner(bool flg, T hoge) {if (flg) {cout << hoge << endl; exit(0);}}
template <class T, class U>ostream &operator<<(ostream &o, const map<T, U>&obj) {o << "{"; for (auto &x : obj) o << " {" << x.first << " : " << x.second << "}" << ","; o << " }"; return o;}
template <class T>ostream &operator<<(ostream &o, const set<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const multiset<T>&obj) {o << "{"; for (auto itr = obj.begin(); itr != obj.end(); ++itr) o << (itr != obj.begin() ? ", " : "") << *itr; o << "}"; return o;}
template <class T>ostream &operator<<(ostream &o, const vector<T>&obj) {o << "{"; for (int i = 0; i < (int)obj.size(); ++i)o << (i > 0 ? ", " : "") << obj[i]; o << "}"; return o;}
template <class T, class U>ostream &operator<<(ostream &o, const pair<T, U>&obj) {o << "{" << obj.first << ", " << obj.second << "}"; return o;}
void print(void) {cout << endl;}
template <class Head> void print(Head&& head) {cout << head;print();}
template <class Head, class... Tail> void print(Head&& head, Tail&&... tail) {cout << head << " ";print(forward<Tail>(tail)...);}
template <class T> void chmax(T& a, const T b){a=max(a,b);}
template <class T> void chmin(T& a, const T b){a=min(a,b);}
void YN(bool flg) {cout << (flg ? "YES" : "NO") << endl;}
void Yn(bool flg) {cout << (flg ? "Yes" : "No") << endl;}
void yn(bool flg) {cout << (flg ? "yes" : "no") << endl;}

int main() {
    int N; cin >> N;
    auto A = multivector(N,N,0);
    int no = 1;
    for(int i = 0; i < N; ++i) {
        string S; cin >> S;
        for(int j = 0; j < N; ++j) A[i][j] = (S[j]=='#');
        for(int j = 0; j < N; ++j) if(S[j]=='#') no = 0;
    }
    corner(no,-1);

    vector<int> sum(N);
    for(int i = 0; i < N; ++i) {
        sum[i] = N - accumulate(ALL(A[i]),0);
    }
    vector<int> flg(N);
    for(int j = 0; j < N; ++j){
        for(int i = 0; i < N; ++i) {
            flg[j] |= A[i][j];
        }
    }
    int all = 0;
    for(int j = 0; j < N; ++j){
        int tmp = 0;
        for(int i = 0; i < N; ++i) {
            tmp += A[i][j];
        }
        all += (tmp==N);
    }
    int ans = 12345678;
    for(int i = 0; i < N; ++i) {
        int cost;
        if(sum[i]) cost = sum[i] + (flg[i]?0:1) + N - all;
        else cost = N - all;
        chmin(ans,cost);
    }
    cout << ans << endl;


    return 0;
}


Measured memory_bytes: 1280