1 #include<bits/stdc++.h>
2 #define ld double
3 using namespace std;
4 const int N=610,M=100010,inf=0x3f3f3f3f;
5 const ld Pi=acos(-1),eps=1e-9;
6 int n,S,T,vis[N],hd[N],o,cur[N],d[N],que[N],head,tail,flow,cnt;
7 ld R,B;
8 struct Edge{int v,nt,f;}E[M<<1];
9 struct poi{ld x,y;}p[N];
10 ld dis(poi A){return sqrt(A.x*A.x+A.y*A.y);}
11 struct data{
12 ld ang;int u,v,t;
13 data(ld _ang=0,int _u=0,int _v=0,int _t=0):ang(_ang),u(_u),v(_v),t(_t){};
14 bool operator <(const data&A)const{return ang==A.ang?t>A.t:ang<A.ang;}
15 }q[N];
16 bool bfs(){
17 for(int i=S;i<=T;++i)vis[i]=0,cur[i]=hd[i];
18 head=tail=0;vis[que[++tail]=S]=d[S]=1;
19 while(head<tail){
20 int u=que[++head];
21 for(int i=hd[u];~i;i=E[i].nt)if(E[i].f){
22 int v=E[i].v;
23 if(vis[v])continue;
24 vis[v]=1;d[v]=d[u]+1;que[++tail]=v;
25 if(v==T)return true;
26 }
27 }
28 return false;
29 }
30 int dfs(int u,int c){
31 if(u==T||!c)return c;
32 int flow=0,f;
33 for(int i=cur[u];~i;i=E[i].nt){
34 int v=E[cur[u]=i].v;
35 if(d[v]==d[u]+1&&(f=dfs(v,min(E[i].f,c)))){
36 flow+=f;c-=f;
37 E[i].f-=f;E[i^1].f+=f;
38 if(!c)break;
39 }
40 }
41 return flow;
42 }
43 void add(int u,int v){
44 E[o]=(Edge){v,hd[u],1};hd[u]=o++;
45 E[o]=(Edge){u,hd[v],0};hd[v]=o++;
46 }
47 void del(int u,int v){
48 int fg=0;
49 for(int i=hd[u];~i;i=E[i].nt)if(E[i].v==v){
50 if(!E[i].f)flow--;else fg=1;
51 E[i].f=E[i^1].f=0;
52 break;
53 }
54 if(fg)return;
55 for(int i=hd[S];~i;i=E[i].nt)if(E[i].v==u){
56 E[i].f=1;E[i^1].f=0;break;
57 }
58 for(int i=hd[v];~i;i=E[i].nt)if(E[i].v==T){
59 E[i].f=1;E[i^1].f=0;break;
60 }
61 if(bfs())flow+=dfs(S,inf);
62 }
63 bool check(ld mid){
64 flow=cnt=o=0;
65 for(int i=S;i<=T;++i)hd[i]=-1;
66 for(int i=1;i<=n;++i){
67 ld d=dis(p[i]);
68 if(mid+d<=R||mid+R<=d)return false;
69 if(R+d<=mid){
70 for(int j=1;j<=n;++j)add(i,j+n);
71 continue;
72 }
73 ld ang=atan2(p[i].y,p[i].x);
74 ld del=acos((d*d+R*R-mid*mid)/(2*d*R));
75 ld ang1=ang-del,ang2=ang+del;
76 while(ang1<0)ang1+=Pi*2;
77 while(ang2<0)ang2+=Pi*2;
78 int l=ang1/B,r=ang2/B;
79 ang1=ang1-B*l;
80 ang2=ang2-B*r;
81 l++;r++;
82 q[++cnt]=(data){ang1,i,l,1};
83 q[++cnt]=(data){ang2,i,r,-1};
84 if(l<=r)for(int j=l+1;j<=r;++j)add(i,j+n);
85 else {
86 for(int j=1;j<=r;++j)add(i,j+n);
87 for(int j=l+1;j<=n;++j)add(i,j+n);
88 }
89 }
90 sort(q+1,q+cnt+1);
91 for(int i=1;i<=n;++i)add(S,i),add(i+n,T);
92 while(bfs())flow+=dfs(S,inf);
93 if(flow==n)return true;
94 for(int i=1;i<=cnt;++i){
95 if(~q[i].t){
96 add(q[i].u,q[i].v+n);
97 if(bfs())flow+=dfs(S,inf);
98 if(flow==n)return true;
99 }
100 else del(q[i].u,q[i].v+n);
101 }
102 return false;
103 }
104 int main(){
105 #ifndef ONLINE_JUDGE
106 freopen("P4518.in","r",stdin);
107 freopen("P4518.out","w",stdout);
108 #endif
109 scanf("%d%lf",&n,&R);
110 B=2*Pi/n;S=0,T=n*2+1;
111 for(int i=1;i<=n;++i)scanf("%lf%lf",&p[i].x,&p[i].y);
112 ld l=0,r=200;
113 while(r-l>eps){
114 ld mid=(l+r)/2;
115 if(check(mid))r=mid;
116 else l=mid;
117 }
118 printf("%.8lf
",l+eps);
119 return 0;
120 }
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