
/*
 * homework3.cpp
 *
 *  Created on: 2012-12-4
 *      Author: Lixurong
 */

int main()
{
	int n, m;
		cin >> n;
		char a[n][n];
		int b[n][n];
		for( int i=0; i<n; i++ )
		{
			for( int j=0; j<n; j++ )
			{
				cin >> a[i][j];
				if( a[i][j]=='.' )
					b[i][j]=0;
				else if( a[i][j]=='#' )
					b[i][j]=-1;
				else
					b[i][j]=1;
			}
		}
		cin >> m;
		m--;
	for( int k=1; k<=m; k++ )
	{
		for( int i=0; i<n; i++ )
		{
			for( int j=0; j<n; j++ )
			{
				if( b[i][j]==k )
				{
					if( b[i][j-1]==0 && j-1>=0 )
					{
						b[i][j-1]=k+1;
					}
					if( b[i][j+1]==0 && j+1<n )
					{
						b[i][j+1]=k+1;
					}
					if( b[i-1][j]==0 && i-1>=0 )
					{
						b[i-1][j]=k+1;
					}
					if( b[i+1][j]==0 && i+1<n )
					{
						b[i+1][j]=k+1;
					}
				}
			}
		}
	}
	int s=0;
	for( int i=0; i<n; i++ )
	{
		for(int j=0; j<n; j++ )
		{
			if( b[i][j]>0 )
				s++;
		}
	}
    cout << s;
	return 0;
}
