#include<bits/stdc++.h>
using namespace std;
int n,k,maxn,c[4]={1,-1,0,0},d[4]={0,0,1,-1};
struct point
{
	int x,y;
}p[501];
bool f[501][501],a[501][501];
void dfs(int step,int left,int x,int y)
{
	for(int j=0;j<4;j++)
	{
		int dx=x+c[j],dy=y+d[j];
		if(!a[dx][dy])
		{
			if(f[dx][dy]) 
			{
				a[dx][dy]=true;
				dfs(step+1,left,dx,dy);
				a[dx][dy]=false;
			}    
		    else if(left>=1)
		         {
		         	 a[dx][dy]=true;
		             dfs(step+1,left-1,dx,dy);
		             a[dx][dy]=false;
	             }
	             else 
				 {
		             maxn=max(maxn,step);
		             return;
	             }
		}
	}
}
int main()
{
	freopen("point.in","r",stdin);
	freopen("point.out","w",stdout);
	cin>>n>>k;
	maxn=k+1;
	for(int i=1;i<=n;i++)
	{
		cin>>p[i].x>>p[i].y;
		f[p[i].x][p[i].y]=true;
	}
	for(int i=1;i<=n;i++)
	{
		a[p[i].x][p[i].y]=true;
		dfs(1,k,p[i].x,p[i].y);
		a[p[i].x][p[i].y]=false;	
	}	
	cout<<maxn;
	return 0;
}