#include <iostream>
#include <cmath>
#include <cstdio>
#include <algorithm>
#include<stack>
using namespace std;
const double pi=acos(-1.00),eps = 1e-6;//pi3.14~
const int N=1001,inf=0x3f3f3f3f;
double ans=0;
struct dot{
    int x,y;
}d[N];
stack<int>s;
int sign(double d)
{
	if(fabs(d)<eps) return 0;
	return d>0? 1:-1;
}
double cross(double x1, double y1, double x2, double y2)
{
	return x1 * y2 - x2 * y1;
}
double length(int x1,int y1,int x2,int y2)
{
	int x=x1-x2,y=y1-y2;
	return sqrt((double)x*x+y*y);//CE double 
}
int main()
{
	int n,l,minn=1,f,ff,x0,x1,x2,y1,y2,y0;
    scanf("%d%d",&n,&l);
    for(int i=1;i<=n;i++)
    {
        scanf("%d%d",&d[i].x,&d[i].y);//&!!!
        minn=d[i].y<d[minn].y? i:minn;
    }
	int j=(n+minn-2)%n+1;
//    s.push(minn%n+1);
    s.push(minn);
    s.push(j);
    ans+=length(d[j].x,d[j].y,d[minn].x,d[minn].y);//漏了初始的边 
    while(j!=minn)
    {
		j=(j+n-2)%n+1;
        f=s.top();
        s.pop();
        ff=s.top();
        while(0>=sign(cross(d[f].x-d[ff].x,d[f].y-d[ff].y,d[j].x-d[ff].x,d[j].y-d[ff].y)))
    	{
    		ans-=length(d[f].x,d[f].y,d[ff].x,d[ff].y);
//    		printf("--%d(%d,%d),%d(%d,%d): -%lf=%lf\n",f,d[f].x,d[f].y,ff,d[ff].x,d[ff].y,length(d[f].x,d[f].y,d[ff].x,d[ff].y),ans);
    		f=s.top();
        	s.pop();
        	if(s.empty()) break;//RE
        	ff=s.top();
		}
		ans+=length(d[j].x,d[j].y,d[f].x,d[f].y);
//    	printf("++%d(%d,%d),%d(%d,%d): +%lf=%lf\n",j,d[j].x,d[j].y,f,d[f].x,d[f].y,length(d[j].x,d[j].y,d[f].x,d[f].y),ans);
		s.push(f);
		s.push(j);
	}
//	printf("%d ",s.size());
	printf("%.0lf",ans+2*l*pi);//WA*2 （周长跟多边形形状有关）错了，无关，自带四舍五入 
	return 0;
}