#include <stdio.h>
#include <string.h>
int n;
char map[5][5] ;
bool visited[5][5] ;
int dir[4][2] = {1,0,-1,0,0,-1,0,1} ;

bool isTrue(int x , int y)
{
	if(x<0||y<0 || x>=n||y>=n )
	{
		return false ;
	}
	return true ;
}

bool judge(int x , int y)
{
	
	int mid = x-1 ;
	while(mid>=0)
	{
		if(map[mid][y]=='*')
		{
			return false ;
		}
		else if(map[mid][y]=='X')
		{
			break ;
		}
		mid-- ;
	}
	mid = x+1 ;
	while(mid<n)
	{
		if(map[mid][y]=='*')
		{
			return false ;
		}
		else if(map[mid][y]=='X')
		{
			break ;
		}
		mid++ ;
	}
	mid = y-1 ;
	while(mid>=0)
	{
		if(map[x][mid]=='*')
		{
			return false ;
		}
		else if(map[x][mid]=='X')
		{
			break ;
		}
		mid-- ;
	}
	mid = y+1 ;
	while(mid<n)
	{
		if(map[x][mid]=='*')
		{
			return false ;
		}
		else if(map[x][mid]=='X')
		{
			break ;
		}
		mid++ ;
	}
	return true ;
}
int ans = 0 ;
void DFS(int pos , int c)
{
	int x = pos/n , y = pos%n ;
	if(c>ans)
	{
		ans = c ;
	}
	for(int i = 0 ; i < 4 ; ++i)
	{
		int nextx = x+dir[i][0] , nexty = y + dir[i][1] ;
		if(visited[nextx][nexty]||!isTrue(nextx,nexty))
		{
			continue ;
		}
		if(judge(nextx,nexty) && map[nextx][nexty]!='X')
		{
			map[nextx][nexty] = '*' ;
			visited[nextx][nexty] = true ;
			DFS(nextx*n+nexty,c+1);
			visited[nextx][nexty] = false ;
			map[nextx][nexty] = '.' ;
		}
		else
		{
			visited[nextx][nexty] = true ;
			DFS(nextx*n+nexty,c);
			visited[nextx][nexty] = false ;
		}
	}
}

int main()
{
	while(~scanf("%d",&n) && n)
	{
		for(int i = 0 ; i < n ; ++i)
		{
			scanf("%s",map[i]) ;
		}
		memset(visited,false,sizeof(visited)) ;
		ans = 0 ;
		for(int i = 0 ; i < n*n ; i++)
		{
			if(map[i/n][i%n]=='.')
			{
				map[i/n][i%n] = '*' ;
				visited[i/n][i%n] = true ;
				DFS(i,1) ; 
				visited[i/n][i%n] = false ;
				map[i/n][i%n] = '.' ;
			}
		}
		printf("%d\n",ans) ;
	}
	return 0 ;
}