#include<bits/stdc++.h>
using namespace std;
const int N = 3e3+5;
const double eps = 1e-5;
int x[N],y[N],f[N];
int n,tx,ty;
double dis(int a,int b){
	return sqrtl(1ll * (x[a]-x[b]) * (x[a]-x[b]) + 1ll * (y[a]-y[b]) * (y[a]-y[b]));
}
int get(int t){
	return f[t] == t ? t : f[t] = get(f[t]);
}
bool check(double t){
	for(int i=0;i<=n+1;i++){
		f[i] = i;
	}
	for(int i=1;i<=n;i++){
		for(int j=i+1;j<=n;j++){
			if(dis(i,j) <= t*2.0){
				int xx = get(i);
				int yy = get(j);
				if(xx != yy){
					f[xx] = yy;
				}
			}
		}
	}
	for(int i=1;i<=n;i++){
		if((double)x[i]-1 <= t){
			int xx = get(0);
			int yy = get(i);
			if(xx != yy){
				f[xx] = yy;
			}
		}
		if((double)y[i]-1 <= t){
			int xx = get(n+1);
			int yy = get(i);
			if(xx != yy){
				f[xx] = yy;
			}
		}
	}
	return get(0) != get(n+1);
}
int main(){
	scanf("%d%d%d",&n,&tx,&ty);
	for(int i=1;i<=n;i++){
		scanf("%d%d",&x[i],&y[i]);
	}
	double l = 0,r = 1e9;
	for(int i=1;i<=50;i++){
		double mid = (l+r)/2.0;
		if(check(mid)){
			l = mid;
		}else{
			r = mid;
		}
	}
	l += eps;
	printf("%.2lf",l);
}