#include <iostream>#include <math.h>using namespace std;const int maxN = 100;const double PI = 3.1415926;int n;double ans,r;struct point{ double x,y; };point pArr[ maxN + 1 ];double dis( point a, point b ){	return sqrt( (a.x - b.x)*(a.x - b.x) + (a.y - b.y)*(a.y - b.y) );}void readIn(){	int i;	cin >> n >> r;	for( i = 1; i <= n; i++ )		{ cin >> pArr[i].x >> pArr[i].y; }}void work(){	int i;	for( i = 1; i < n; i++ )		ans += dis( pArr[i],pArr[i+1] );	ans += dis( pArr[i],pArr[1] );	ans += 2*PI*r;}int main(){//	freopen("1020.in","r",stdin);	readIn();	work();	cout.setf(ios::fixed);	cout.precision(2);	cout << ans << endl;	return 0;}