#include <cstdio>
#include <cstring>
using namespace std;
char Ap[5][5];
int Gra[5][5], vis[5], dis[5];
int dx[5], dy[5], left[5], right[5];
int n;
struct Node{
    int x, y;
}a[5][5];
void Printf(){
    for(int i = 0; i < n; i++){
        for(int j = 0; j < n; j++){
            printf("%c", Ap[i][j]);
        }
        printf("\n");
    }
}
int x, y;
bool Search(int a){
    for(int i = 1; i <= y; i++){
        if(Gra[a][i] && !vis[i]){
            vis[i] = 1;
            if(!dis[i] || Search(dis[i])){
                dis[i] = a; 
                return true;
            }
        }
    }
    return false;
}
int main(){
    while(scanf("%d", &n) != EOF && n){
        for(int i = 0; i < n; i++)
        {
            getchar(); 
            for(int j = 0; j < n; j++)
                scanf("%c", &Ap[i][j]);
        }
        x = y = 0;
        for(int i = 0; i < n; i++)   //行列匹配； 
            for(int j = 0; j < n; j++)
            {
                if(Ap[i][j] == ‘.‘)  
                {
                    if(j == 0 || Ap[i][j-1] == ‘X‘){
                        x++;        /***********************/
                    }
                    a[i][j].x = x;  
                }
                if(Ap[j][i] == ‘.‘)
                {
                    if(j == 0 || Ap[j-1][i] == ‘X‘){
                        y++;       /***********************/
                    }
                    a[j][i].y = y; 
                }
            }
        memset(Gra, 0, sizeof(Gra));
        for(int i = 0; i < n; i++)
            for(int j = 0; j < n; j++){
                if(Ap[i][j] == ‘.‘){
                    int u = a[i][j].x;
                    int v = a[i][j].y;
                    Gra[u][v] = 1;
                }
            }
        int ans = 0;
        memset(dis, 0, sizeof(dis));
        for(int i = 1; i <= x; i++)
        {
            memset(vis, 0, sizeof(vis));
            if(Search(i))
                ans++;
        }
        printf("%d\n", ans); 
    }
    return 0;
} 

#include <cstdio>
int n, cnt;
char map[5][5];
bool Build(int row, int col){
    int i, j;
    for(int i = row; i >= 0; i--){
        if(map[i][col] == ‘O‘)
            return false;
        if(map[i][col] == ‘X‘)
            break;
    }
    for(int i = col; i >= 0; i--){
        if(map[row][i] == ‘O‘)
            return false;
        if(map[row][i] == ‘X‘)
            break;
    }
    return true ;
} 
void Dfs(int i, int num){
    if(i == n*n){
    //    printf("%d %d\n", i, num);
        if(num > cnt)
            cnt = num;
        return;
    }
    else{
        int row = i / n;
        int col = i % n;
        if(map[row][col] == ‘.‘ && Build(row, col)){
            map[row][col] = ‘O‘;
            Dfs(i+1, num+1);
            map[row][col] = ‘.‘;
        } 
        Dfs(i+1, num);
    }
}
int main(){
    while(scanf("%d", &n), n){
        cnt = 0;
        for(int i = 0; i < n; i++)
            scanf("%s", map[i]);
        Dfs(0, 0);
        printf("%d\n", cnt);
    }    
    return 0;
}