#include "bits/stdc++.h"
using namespace std;

#define DEBUG(x) cout<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cout<<#v<<":";for(int i=0;i<v.size();i++) cout<<" "<<v[i]; cout<<endl

typedef long long ll;
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
const int inf = 1000000001;
const ll INF = 2e18 * 2;
#define MOD 1000000007
#define mod 1000000009
#define pi 3.14159265358979323846
#define Sp(p) cout<<setprecision(15)<< fixed<<p<<endl;
int dx[4] = { 1,0,-1,0 }, dy[4] = { 0,1,0,-1 };
int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };

int ans = 0;
int n;

void dfs(vector<vector<char> > s, int nowi, int nowj, int cnt) {
	if (nowj == n) {
		ans = max(ans, cnt);
		return;
	}
	int nexti, nextj;
	if (nowj < 2) {
		if (nowi < n - 1) {
			nexti = nowi + 1;
			nextj = nowj;
		}
		else {
			nexti = 0;
			nextj = nowj + 1;
		}
	}
	else {
		if (nowi == 0) {
			nexti = 1;
			nextj = nowj;
		}
		else {
			nexti = 0;
			nextj = nowj + 1;
		}
	}
	if (nowi < 2) {
		auto s2 = s;
		bool flag = true;
		for (int i = 0; i < n - 1; i++) {
			if (s2[nowi + i][nowj] == '#') {
				flag = false;
				break;
			}
			s2[nowi + i][nowj] = '#';
		}
		if (flag) {
			dfs(s2, nexti, nextj, cnt + 1);
		}
	}
	if (nowj < 2) {
		auto s2 = s;
		bool flag = true;
		for (int j = 0; j < n - 1; j++) {
			if (s2[nowi][nowj + j] == '#') {
				flag = false;
				break;
			}
			s2[nowi][nowj + j] = '#';
		}
		if (flag) {
			dfs(s2, nexti, nextj, cnt + 1);
		}
	}
	dfs(s, nexti, nextj, cnt);
}

int main() {
	int i, j;
	cin >> n;
	vector<vector<char> > s(n, vector<char>(n));
	for (i = 0; i < n; i++) {
		for (j = 0; j < n; j++) {
			cin >> s[i][j];
		}
	}
	dfs(s, 0, 0, 0);
	cout << ans << endl;
}