1 /**************************************************************
 2     Problem: 3007
 3     User: Tunix
 4     Language: C++
 5     Result: Accepted
 6     Time:1176 ms
 7     Memory:72104 kb
 8 ****************************************************************/
 9  
10 //Huce #3 A
11 #include<cmath>
12 #include<queue>
13 #include<vector>
14 #include<cstdio>
15 #include<cstdlib>
16 #include<cstring>
17 #include<iostream>
18 #include<algorithm>
19 #define rep(i,n) for(int i=0;i<n;++i)
20 #define F(i,j,n) for(int i=j;i<=n;++i)
21 #define D(i,j,n) for(int i=j;i>=n;--i)
22 using namespace std;
23  
24 int getint(){
25     int v=0,sign=1; char ch=getchar();
26     while(ch<‘0‘||ch>‘9‘) {if (ch==‘-‘) sign=-1; ch=getchar();}
27     while(ch>=‘0‘&&ch<=‘9‘) {v=v*10+ch-‘0‘; ch=getchar();}
28     return v*sign;
29 }
30 typedef long long LL;
31 const int N=3010,INF=~0u>>2;
32 const double eps=1e-5;
33 /*******************tamplate********************/
34 struct Boss{
35     int x,y;
36     Boss(){}
37     Boss(int x,int y):x(x),y(y){}
38     void read(){scanf("%d%d",&x,&y);}
39 }boss[N];
40 double inf = 1 << 25,g[N][N],f[N];
41 int n,row,line;
42 double dis(Boss a,Boss b){
43     double x,y;
44     x=a.x-b.x; y=a.y-b.y;
45     return sqrt(x*x+y*y);
46 }
47 void build(){
48     F(i,1,n+4) F(j,1,n+4) g[i][j]=inf;
49     F(i,1,n) F(j,i+1,n)
50         g[i][j]=g[j][i]=dis(boss[i],boss[j])/2;
51     F(i,1,n){
52         g[n+1][i]=boss[i].y-1;
53         g[n+2][i]=row-boss[i].x;
54         g[i][n+3]=line-boss[i].y;
55         g[i][n+4]=boss[i].x-1;
56     }
57 }
58  
59 bool vis[N];
60 double solve(){
61     memset(vis,0,sizeof vis);
62     F(i,1,n+4) f[i]=inf;
63     f[n+1]=f[n+2]=0;
64     vis[n+1]=vis[n+2]=1;
65     double mn; int l;
66     while(1){
67         mn=inf; l=-1;
68         F(i,1,n+4) if (vis[i] && f[i]<mn){
69             mn=f[i]; l=i;
70         }
71         if (l==-1) break;
72         F(i,1,n+4)
73             if (max(g[l][i],f[l])<f[i]){
74                 f[i]=max(g[l][i],f[l]);
75                 vis[i]=1;
76             }
77         vis[l]=0;
78     }
79     return min(f[n+3],f[n+4]);
80 }
81 int main(){
82 #ifndef ONLINE_JUDGE
83     freopen("input.txt","r",stdin);
84 //  freopen("output.txt","w",stdout);
85 #endif
86     n=getint(); row=getint(); line=getint();
87     F(i,1,n) boss[i].read();
88     double ans=inf;
89     F(i,1,n){
90         ans=min(ans,dis(Boss(1,1),boss[i]));
91         ans=min(ans,dis(Boss(row,line),boss[i]));
92         //用起始位置和结束位置更新答案
93     }
94     build();
95     ans=min(ans,solve());
96     printf("%.2lf\n",ans);
97     return 0;
98 }