1 #include <stdio.h> 2 #include <string.h> 3 #include <iostream> 4 #include <cmath> 5 #include <algorithm> 6  7 const double PI = acos(-1.0) ; 8 using namespace std ; 9 10 struct point11 {12     double x,y ;13 }p[110],p1[110];14 int n ,m;15 16 double dis(point a,point b)17 {18     return sqrt(double((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y))) ;19 }20 double cross(point a,point b,point c)21 {22     return (a.x-c.x)*(b.y-c.y) - (a.y-c.y)*(b.x-c.x) ;23 }24 bool cmp(point a,point b)25 {26     if(cross(a,b,p[0]) > 0 || cross(a,b,p[0]) == 0 && dis(a,p[0]) < dis(b,p[0]))27         return true ;28     return false ;29 }30 void Graham()31 {32     int cnt;33     sort(p+1,p+n,cmp) ;34     p[n] = p[0] ;35     p1[0] = p[0] ;36     p1[1] = p[1] ;37     cnt = 1 ;38     for(int i = 2 ; i <= n ; i++)39     {40         while(cnt >= 1 && cross(p1[cnt-1],p1[cnt],p[i]) <= 0) cnt -- ;41         p1[ ++cnt] = p[i] ;42     }43     double sum = 0.0 ;44     for(int i = 0 ; i < cnt ; i++)45         {46             sum += dis(p1[i],p1[i+1]) ;47         }48         printf("%.0lf\n",sum+2*PI*m) ;49 }50 int main()51 {52     while(~scanf("%d %d",&n,&m))53     {54         int pos = 0 ;55         for(int i = 0 ; i < n ; i++)56         {57             scanf("%lf %lf",&p[i].x,&p[i].y) ;58             if(p[pos].y > p[i].y || (p[pos].y == p[i].y && p[i].x < p[pos].x))59                 pos = i ;60         }61 //        if(n == 1) {puts("0.00");continue ;}62 //        if(n == 2)63 //        {64 //            printf("%.2lf\n",dis(p[1],p[0])) ;65 //            continue ;66 //        }67         swap(p[pos],p[0]) ;68         //printf("%d %d\n",p[0].x,p[0].y) ;69         Graham() ;70     }71     return 0 ;72 }