#include<map>

#include<set>

#include<cmath>

#include<queue>

#include<stack>

#include<vector>

#include<cstdio>

#include<cassert>

#include<iomanip>

#include<cstdlib>

#include<cstring>

#include<iostream>

#include<algorithm>

#define pi acos(-1.0)

#define ll long long

#define mod 1000000007

#define ls l,m,rt<<1

#define rs m+1,r,rt<<1|1

#pragma comment(linker, "/STACK:1024000000,1024000000")

using namespace std;

const double g=10.0,eps=1e-;

const int N=+,maxn=+,inf=0x3f3f3f;

struct point{

    double x,y;

};

point p[N],s[N];

int top,n;

double dir(point p1,point p2,point p3)

{

    return (p3.x-p1.x)*(p2.y-p1.y)-(p3.y-p1.y)*(p2.x-p1.x);

}

double dis(point a,point b)

{

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

}

bool comp(point a,point b)

{

    int te=dir(p[],a,b);

    if(te<)return ;

    if(te==&&dis(p[],a)<dis(p[],b))return ;

    return ;

}

void graham()

{

    int pos,minx,miny;

    minx=miny=inf;

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

    {

        if(p[i].x<minx||(p[i].x==minx&&p[i].y<miny))

        {

            minx=p[i].x;

            miny=p[i].y;

            pos=i;

        }

    }

    swap(p[],p[pos]);

    sort(p+,p+n,comp);

    p[n]=p[];

    s[]=p[],s[]=p[],s[]=p[];

    top=;

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

    {

        while(dir(s[top-],s[top],p[i])>=&&top>=)top--;

        s[++top]=p[i];

    }

}

int main()

{

    ios::sync_with_stdio(false);

    cin.tie();

    int l;

    cin>>n>>l;

    for(int i=;i<n;i++)cin>>p[i].x>>p[i].y;

    graham();

    double ans=*pi*l;

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

    {

     //   cout<<s[i].x<<" "<<s[i].y<<endl;

        if(i==top-)ans+=dis(s[i],s[]);

        else ans+=dis(s[i],s[i+]);

    }

    cout<<(int)(ans+0.5)<<endl;

    return ;

}

/*

4 3

0 0

1 0

0 1

1 1

*/