#include<cstdio>

 #include<cstring>

 #include<cstdlib>

 #include<cmath>

 #include<algorithm>

 using namespace std;

 const int maxn=;

 const double pi=acos(-1.0);

 struct point

 {

     double x,y;

     bool operator <(const point &a)const

     {

         return (x<a.x)||(x==a.x&&y<a.y);

     }

 }p[maxn],ch[maxn];

 double sqr(double x)

 {

     return x*x;

 }

 double det(point a,point b,point c)

 {

     return ((b.x-a.x)*(c.y-a.y)-(c.x-a.x)*(b.y-a.y));

 }

 double dis(point a,point b)

 {

     return sqrt(sqr(a.x-b.x)+sqr(a.y-b.y));

 }

 int convex_hull(point *p,int n,point *ch)

 {

     sort(p,p+n);

     int m=;

     for(int i=; i<n; i++)

     {

         while(m>&&det(ch[m-],ch[m-],p[i])<=) m--;

         ch[m++]=p[i];

     }

     int k=m;

     for(int i=n-; i>=; i--)

     {

         while(m>k&&det(ch[m-],ch[m-],p[i])<=) m--;

         ch[m++]=p[i];

     }

     if(n>) m--;

     return m;

 }

 double diss(point *ch,int n)

 {

     double sum=;

     for(int i=; i<n; i++)

     {

         sum+=dis(ch[i],ch[i-]);

     }

     return sum;

 }

 int main()

 {

     int n,l;

     scanf("%d%d",&n,&l);

     for(int i=; i<n; i++)

     {

         scanf("%lf%lf",&p[i].x,&p[i].y);

     }

     int cn=convex_hull(p,n,ch);

     printf("%.lf\n",(diss(ch,cn+)+*pi*l));

     return ;

 }