int main()
{
	int n, m, sum = 0;
	int room[102][102];
	char ch;
	int i,j,k;
	scanf("%d", &n);
	for (i = 1; i <= n; i++)
	{
		getchar();
		for (j = 1; j <= n; j++)
		{
			scanf("%c", &ch);
			if (ch == '#')
				room[i][j] = -1;
			else if (ch == '.')
				room[i][j] = 0;
			else if (ch == '@')
				room[i][j] = 1;
		}
	}
	int nn = n+1;
	for (i = 0; i <= nn; i++)
		room[i][0] = room[0][i] = room[i][nn] = room[nn][i] = -1;
	scanf("%d", &m);
	for (k = 1; k < m; k++)
		for (i = 1; i <= n; i++)
			for (j = 1; j <= n; j ++)
				if (room[i][j] == k)
				{
					if (room[i+1][j] == 0) 
						room[i+1][j] = k+1;
					if (room[i-1][j] == 0) 
						room[i-1][j] = k+1;
					if (room[i][j+1] == 0) 
						room[i][j+1] = k+1;
					if (room[i][j-1] == 0) 
						room[i][j-1] = k+1;
				}
	for (i = 1; i <= n; i++)
		for (j = 1; j <= n; j++)
			if (room[i][j] > 0)
				sum++;
	printf("%d\n", sum);
	return 0;
}