#include<stdio.h>#include<math.h>struct node{double x;double y;}p[105];const double PI = acos(-1.0);double dis(int a,int b){double c = p[a].x - p[b].x,d = p[a].y - p[b].y;return sqrt(c*c+d*d);} int main(){int i,n;double r,result;while(~scanf("%d%lf",&n,&r)){result = 0.0;for(i = 1;i <= n;i ++) scanf("%lf%lf",&p[i].x,&p[i].y);for(i = 2;i <= n;i ++) result += dis(i-1,i);result += dis(1,n);result += 2*PI*r; printf("%.2fn",result);}return 0;}
