#include <stdio.h>

int Put ( int x, int y );
void Out ( int a, int b );

char z[10][10];
int n, max;

int main()
{
    int i;
    while( scanf( "%d", &n ) != EOF )
    {
        if( n == 0 )
            break;
        for( i = 0; i < n; i++ )
                scanf( "%s", z[i] );
        max = 0;
        Out(0,0);

        printf( "%d\n", max );
    }
}

int Put( int x, int y )
{
    int i;

    if( z[x][y] != '.' )
        return 0;

    for( i = x-1; i >= 0; i-- )
    {
        if( z[i][y] == 'X' )
            break;

        if( z[i][y] == '0' )
            return 0;
    }

    for( i = y-1; i >= 0; i-- )
    {
        if( z[x][i] == 'X' )
            break;

        if( z[x][i] == '0' )
            return 0;
    }

    return 1;
}
void Out ( int a, int b )
{
    int x, y;
    if( a >= n*n )
        {
            if( max < b ) max = b;
            return;
        }

    x = a / n;
    y = a % n;

    if( Put( x, y ) == 1 )
    {
        z[x][y] = '0';

        Out( a+1, b+1 );

        [color=#00FF00]z[x][y] = '.';
    }

    Out( a+1, b );
}
[/color]