/*
ID: LinKArftc
PROG: 1045.cpp
LANG: C++
*/

#include <map>
#include <set>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <cstdio>
#include <string>
#include <utility>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
#define eps 1e-8
#define randin srand((unsigned int)time(NULL))
#define input freopen("input.txt","r",stdin)
#define debug(s) cout << "s = " << s << endl;
#define outstars cout << "*************" << endl;
const double PI = acos(-1.0);
const double e = exp(1.0);
const int inf = 0x3f3f3f3f;
const int INF = 0x7fffffff;
typedef long long ll;

const int maxn = 20;

struct Node {
    char cha;
    int idx, idy;
} node[maxn][maxn];
int mp[maxn][maxn];
int n, uN, vN;
int linker[maxn];
bool vis[maxn];

bool dfs(int u) {
    for (int v = 1; v <= vN; v ++) {
        if (!vis[v] && mp[u][v]) {
            vis[v] = true;
            if (linker[v] == -1 || dfs(linker[v])) {
                linker[v] = u;
                return true;
            }
        }
    }
    return false;
}

int hungry() {
    memset(linker, -1, sizeof(linker));
    int ret = 0;
    for (int i = 1; i <= uN; i ++) {
        memset(vis, 0, sizeof(vis));
        if (dfs(i)) ret ++;
    }
    return ret;
}

int main() {

    while (~scanf("%d", &n) && n) {
        for (int i = 1; i <= n; i ++) {
            for (int j = 1; j <= n; j ++) scanf(" %c", &node[i][j].cha);
        }
        uN = 0;
        for (int i = 1; i <= n; i ++) {
            for (int j = 1; j <= n; j ++) {
                if (node[i][j].cha == ‘X‘) continue;
                if (j == 1 && node[i][j].cha == ‘.‘) uN ++;
                else if (node[i][j].cha == ‘.‘ && node[i][j-1].cha == ‘X‘) uN ++;
                node[i][j].idx = uN;
            }
        }
        vN = 0;
        for (int j = 1; j <= n; j ++) {
            for (int i = 1; i <= n; i ++) {
                if (node[i][j].cha == ‘X‘) continue;
                if (i == 1 && node[i][j].cha == ‘.‘) vN ++;
                else if (node[i][j].cha == ‘.‘ &&node[i-1][j].cha == ‘X‘) vN ++;
                node[i][j].idy = vN;
            }
        }
        memset(mp, 0, sizeof(mp));
        for (int i = 1; i <= n; i ++) {
            for (int j = 1; j <= n; j ++) {
                if (node[i][j].cha == ‘X‘) continue;
                mp[node[i][j].idx][node[i][j].idy] = 1;
            }
        }
        printf("%d\n", hungry());
    }

    return 0;
}