#include<bits/stdc++.h>
using namespace std;
long long n,m,id;
int main()
{
	double r,x,y,z,k,l,a,b,C,t,ans=0;
	cin>>n>>r;
	cin>>k>>t;
	a=k;
	b=t;
	for (int i=2;i<=n;i++)
	{
		cin>>x>>y;
		ans+=sqrt((x-k)*(x-k)+(y-t)*(y-t));
		k=x;
		t=y;
	}
	C=3.141*r*2;
	ans+=C;
	ans+=sqrt((a-k)*(a-k)+(b-t)*(b-t));
	printf("%0.2lf",ans);
	return 0;
}

#include<bits/stdc++.h>
#define f(i,l,r) for(int i=l;i<=r;i++)
using namespace std;
int n;
double ri;
double ans;
struct fff{
	double a,b;
}x[10005];
double jl(double x,double y,double xl,double yl){
	return sqrt((xl-x)*(xl-x)+(yl-y)*(yl-y));
}
int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);cout.tie(0);
	cin>>n>>ri;
	f(i,1,n){
		cin>>x[i].a>>x[i].b;
	}
	f(i,1,n-1){
		ans=ans+jl(x[i].a,x[i].b,x[i+1].a,x[i+1].b);
	}
	ans=ans+jl(x[n].a,x[n].b,x[1].a,x[1].b);
	ans=ans+3.1415926535*ri*2;
	printf("%.2lf",ans);
	return 0;
}