Description：

Solution：

Code：

#include<algorithm>

#include<iostream>

#include<cstdlib>

#include<cstdio>

#include<cmath>

#include<cctype>

#include<cstring>

using namespace std;

int n;

double a,b,r;

#define MAXN 10010

struct point

{

    double x,y;

}p[MAXN * 4];

bool cmp_x(point a,point b){return a.x < b.x;}

bool equal(double a,double b){return fabs(a - b) < 1e-9;}

int tot = 0;

point rotate(point k,double th)

{

    point res;

    res.x = k.x * cos(th) - k.y * sin(th);

    res.y = k.x * sin(th) + k.y * cos(th);

    return res; 

}

point us[MAXN * 4],ds[MAXN * 4];

int utop = 0,dtop = 0;

double slope(point a,point b){return (b.y - a.y) / (b.x - a.x);}

double dis(point a,point b){return sqrt((b.y - a.y) * (b.y - a.y) + (b.x - a.x) * (b.x - a.x));}

int main()

{

    scanf("%d",&n);

    scanf("%lf%lf%lf",&a,&b,&r);

    a = a / 2 - r;b = b / 2 - r;

    double x,y,th;

    for(int i = 1;i <= n;++i)

    {

        scanf("%lf%lf%lf",&x,&y,&th);

        p[++tot] = rotate((point){b,a},th);p[tot].x += x;p[tot].y += y;

        p[++tot] = rotate((point){-b,a},th);p[tot].x += x;p[tot].y += y;

        p[++tot] = rotate((point){b,-a},th);p[tot].x += x;p[tot].y += y;

        p[++tot] = rotate((point){-b,-a},th);p[tot].x += x;p[tot].y += y;

    }

    sort(p + 1,p + 1 + tot,cmp_x);

    for(int i = 1;i <= tot;++i)

    {

        if(utop >= 1 && equal(us[utop].x,p[i].x))

        {

            if(p[i].y > us[utop].y)--utop;

            else continue;

        }

        if(utop <= 1)us[++utop] = p[i];

        else

        {

            while(utop >= 2 && slope(p[i],us[utop]) >= slope(us[utop],us[utop - 1]))--utop;

            us[++utop] = p[i];

        }

    }

    for(int i = 1;i <= tot;++i)

    {

        if(dtop >= 1 && equal(ds[dtop].x,p[i].x))

        {

            if(p[i].y < ds[dtop].y)--dtop;

            else continue;

        }

        if(dtop <= 1)ds[++dtop] = p[i];

        else

        {

            while(dtop >= 2 && slope(p[i],ds[dtop]) <= slope(ds[dtop],ds[dtop - 1]))--dtop;

            ds[++dtop] = p[i];

        }

    }

    double ans = 0;

    for(int i = 1;i < utop;++i)ans += dis(us[i],us[i + 1]);

    for(int i = 1;i < dtop;++i)ans += dis(ds[i],ds[i + 1]);

    ans += dis(us[1],ds[1]);ans += dis(us[utop],ds[dtop]);

    ans = ans + 2 * acos(-1) * r;

    printf("%.2lf\n",ans);

    return 0;

}