/*
TASK:colxor
LANG:C++
*/
#include<stdio.h>
int N,R,i,u,a,j,n,x,y;
int XY[1000][1000],A[1000];
int main()
{int k,br=0;
scanf("%d%d",&N,&R);
int f=0,w=0;
for (u=1;u<=N;u++)
	{scanf("%d%d",&x,&y);
	x+=500;
	y+=500;
	f++;
	for (w;w<f;w++)
	A[w]=y;
	for (i=(x-(R-1));i<(x+(1+R));i++)
		for (j=(y-(R-1));j<(y+(R+1));j++)
			if (XY[i][j]==0) XY[i][j]=1;
			   else XY[i][j]=0;

}

  k=(R/N+1)*4;


  for (i=1;i<=1000;i++)
   for (j=1;j<=1000;j++)
	if (XY[i][j]==1)
	 br++;

 if (N>1) printf ("%d\n",br-k);
 else printf ("%d\n",(br-4*(R/2+1)));
return 0;
}
