#include <stdio.h>
#include <algorithm>
#include <math.h>
#define N_MAX 1000
#define Pi 3.1415926535897932384626433832795
using namespace std;
struct column {
int x;
int y;
bool operator < (column K) const {return x<K.x || (x==K.x && y<K.y);}
} A[N_MAX+1];
int N, R, Up[N_MAX+1], Usize, Down[N_MAX+1], Dsize;
double Res;
int turn(int a, int b, int c) {return (A[a].x*A[b].y+A[b].x*A[c].y+A[c].x*A[a].y)-(A[b].x*A[a].y+A[c].x*A[b].y+A[a].x*A[c].y);}
int main(void) {
int i;
scanf("%d %d",&N,&R);
for(i=1 ; i<=N ; i++) scanf("%d %d",&A[i].x,&A[i].y);
sort(A+1,A+N+1);
Up[++Usize]=1;
Up[++Usize]=2;
Down[++Dsize]=1;
Down[++Dsize]=2;
for(i=3 ; i<=N ; i++) {
while(Usize>=2 && turn(Up[Usize-1],Up[Usize],i)>=0) Usize--;
Up[++Usize]=i;
while(Dsize>=2 && turn(Down[Dsize-1],Down[Dsize],i)<=0) Dsize--;
Down[++Dsize]=i;
}
for(i=2 ; i<=Usize ; i++) Res+=sqrt((A[Up[i]].x-A[Up[i-1]].x)*(A[Up[i]].x-A[Up[i-1]].x)+(A[Up[i]].y-A[Up[i-1]].y)*(A[Up[i]].y-A[Up[i-1]].y));
for(i=2 ; i<=Dsize ; i++) Res+=sqrt((A[Down[i]].x-A[Down[i-1]].x)*(A[Down[i]].x-A[Down[i-1]].x)+(A[Down[i]].y-A[Down[i-1]].y)*(A[Down[i]].y-A[Down[i-1]].y));
Res+=2*Pi*R;
printf("%.12lf",Res);
return 0;
}
