#include<cstdio>
#include<cstring>
#include<cmath>
#include<cstdlib>
#include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
#include<stack>
#include<string>
#include<set>
#include<ctime>
#define eps 1e-6
#define LL long long
#define pii pair<int, int>
//#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;

const int MAXN = 1505;//這個值要超過兩邊個數的較大者，因為有linker
int linker[MAXN];
bool used[MAXN];
vector<int> map[MAXN];
int uN, uV;
bool dfs(int u)
{
	for (int i = 0; i < map[u].size(); i++)
	{
		int v = map[u][i];
		if(!used[v])
		{
			used[v] = 1;
			if(linker[v]==-1 || dfs(linker[v])) {
				linker[v] = u;
				return true;
			}
		}
	}
	return false;
}
int hungary()
{
	int res = 0;
	memset(linker, -1, sizeof(linker));
	int u;
	for (u = 0; u < uN; u++)
	{
        memset(used, 0, sizeof(used));
        if(dfs(u)) res++;
	}
	return res;
}
int n;
char G[5][5];
int idX[5][5], idY[5][5];
int main()
{
    //freopen("input.txt", "r", stdin);
	while(cin>>n && n)
    {
        for (int i = 1; i <= n; i++)
        {
            char row[10];
            scanf("%s", row);
            for (int j = 1; j <= n; j++)
            {
                G[i][j] = row[j-1];
            }
        }
        uN = uV = 0;
        for(int i = 1; i <= n; i++)
        {
            G[i][0] = 'X';
            for(int j = 1; j <= n; j++)
            {
                if(G[i][j] == '.')
                {
                    idX[i][j] = uN;
                }
                else if(G[i][j]=='X' && G[i][j-1]!='X')
                {
                    uN++;
                }
            }
            if(G[i][n] != 'X') uN++;
        }
        for(int i = 1; i <= n; i++)
        {
            G[0][i] = 'X';
            for(int j = 1; j <= n; j++)
            {
                if(G[j][i] == '.')
                {
                    idY[j][i] = uV;
                }
                else if(G[j][i]=='X' && G[j-1][i]!='X')
                {
                    uV++;
                }
            }
            if(G[n][i] != 'X') uV++;
        }
        for(int i = 0; i < uN; i++)
            map[i].clear();
        for(int i = 1; i <= n; i++)
        {
            for(int j = 1; j <= n; j++)
            {
                if(G[i][j] == '.')
                {
                    map[idX[i][j]].push_back(idY[i][j]);
                }
            }
        }
        int ans = hungary();
        cout << ans << endl;
	}
    return 0;
}