#include <iostream>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <math.h>#include <algorithm>using namespace std;#define maxn 1005struct point{ double x, y;} pnt[maxn], res[maxn];int n, l;bool mult(point sp, point ep, point op){ return (sp.x - op.x) * (ep.y - op.y) >= (ep.x - op.x) * (sp.y - op.y);}bool operator<(const point &l, const point &r){ return l.y < r.y || (l.y == r.y && l.x < r.x);}int graham(point pnt[], int n, point res[]){ int i, len, top =1; sort(pnt, pnt + n); if (n ==0) return 0; res[0] = pnt[0]; if (n ==1) return 1; res[1] = pnt[1]; if (n ==2) return 2; res[2] = pnt[2]; for (i =2; i < n; i++) { while (top && mult(pnt[i], res[top], res[top -1])) top--; res[++top] = pnt[i]; } len = top; res[++top] = pnt[n -2]; for (i = n -3; i >=0; i--) { while (top != len && mult(pnt[i], res[top], res[top -1])) top--; res[++top] = pnt[i]; } return top;}double dis(point &p, point &q){ double x1 = p.x - q.x, y1 = p.y - q.y; return sqrt(x1 * x1 + y1 * y1);}int main(){ scanf("%d%d", &n, &l); for (int i =0; i < n; i++) scanf("%lf%lf", &pnt[i].x, &pnt[i].y); int tot = graham(pnt, n, res); double ans = l *2*3.14159265; for (int i =0; i < tot; i++) ans += dis(res[i], res[(i +1) % tot]); printf("%.0fn", ans); return 0;}
