#include<iostream>

#include<algorithm>

#include<cmath>

using namespace std;

typedef pair<int ,int > ll;

ll num,dot[1010];

int i;

const double pi=3.1415926535898;

ll operator -(ll a,ll b)

{

	return make_pair(a.first-b.first,a.second-b.second);

}

bool cmp(ll a,ll b)

{

	return (a.first!=b.first?a.first<b.first:a.second<b.second);

}

int cross(ll a,ll b)

{

	return a.first*b.second-b.first*a.second;

}

int d2(ll a,ll b)

{

	return (a.first-b.first)*(a.first-b.first)+(a.second-b.second)*(a.second-b.second);

}

double d1(ll a,ll b)

{

	return sqrt((double)d2(a,b));

}

bool cmp1(ll a,ll b)

{

	int r=cross(a-dot[0],b-dot[0]);

	return (r!=0?r>0:d2(a,dot[0])<d2(b,dot[0]));

}

void in()

{

	cin>>num.first>>num.second;

	for(i=0;i<num.first;i++)

		cin>>dot[i].first>>dot[i].second;

}

void work()

{

	sort(dot,dot+num.first,cmp);

	sort(dot,dot+num.first,cmp1);

	ll box[1010]={dot[0],dot[1]};

	int tail=1;

	for(i=2;i<num.first;)

	{

		if(cross(box[tail]-box[tail-1],dot[i]-box[tail-1])>=0)

			box[++tail]=dot[i++];

		else

			tail--;

	}

	double ans=d1(box[0],box[tail])+2*pi*num.second;

	for(i=0;i<tail;i++)

		ans+=d1(box[i],box[i+1]);

	printf("%.0lf\n",ans);

}

int main()

{

	in();

	work();

}