> #include<stdio.h>
> #include<math.h>
> struct point
> {
> 	int x;
> 	int y;
> }mypoint[1000],temp,stack[3000],x,y,z;
> int main()
> {
> 	int n,l,number,top,t,i,j;
> 	while(scanf("%d%d",&n,&l)==2)
> 	{
> 		for(i=0;i<n;i++) scanf("%d%d",&mypoint[i].x,&mypoint[i].y);
> 		for(i=0;i<n-1;i++)
> 			for(j=0;j<n-1-i;j++)
> 				if(mypoint[j].y>mypoint[j+1].y
> 					||(mypoint[j].y==mypoint[j+1].y&&mypoint[j].x>mypoint[j+1].x))
> 				{
> 					temp=mypoint[j];
> 					mypoint[j]=mypoint[j+1];
> 					mypoint[j+1]=temp;
> 				}
> 		number=1;stack[0]=mypoint[0];top=0;
> 		for(i=1;i<n;i++)
> 		{
> 			if(number==1)
> 			{
> 				number++;
> 				top++;
> 				stack[top]=mypoint[i];
> 				continue;
> 			}
> 			z=mypoint[i];
> 			y=stack[top];
> 			x=stack[top-1];
> 			t=(y.x-x.x)*(z.y-y.y)-(y.y-x.y)*(z.x-y.x);
> 			if(t>0)
> 			{
> 				number++;
> 				top++;
> 				stack[top]=mypoint[i];
> 				continue;
> 			}
> 			top--;number--;i--;
> 		}
> 		for(i--;i>=0;i--)
> 		{
> 			for(j=0;j<=top;j++) if(stack[j].x==mypoint[i].x&&stack[j].y==mypoint[i].y) break;
> 			if(j>top||i==0)
> 			{
> 				z=mypoint[i];
> 				y=stack[top];
> 				x=stack[top-1];
> 				t=(y.x-x.x)*(z.y-y.y)-(y.y-x.y)*(z.x-y.x);
> 				if(t>0)
> 				{
> 					number++;
> 					top++;
> 					stack[top]=mypoint[i];
> 					continue;
> 				}
> 				top--;number--;i++;
> 			}
> 		}
> 		//for(i=0;i<=top;i++) printf("%d %d\n",stack[i].x,stack[i].y);
> 		double pi=3.1415926,sum=0;
> 		for(i=1;i<=top;i++) 
> 			sum+=sqrt((stack[i].x-stack[i-1].x)*(stack[i].x-stack[i-1].x)+(stack[i].y-stack[i-1].y)*(stack[i].y-stack[i-1].y));
> 		sum+=pi*2*l;
> 		printf("%.0lf\n",sum);
> 	}
> 	return 0;
> }
> 
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