package yukicoder094;

import java.util.Arrays;
import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		double[] x=new double[n];
		double[] y=new double[n];
		UnionFind uni=new UnionFind(n);
		for(int i=0;i<n;i++){
			x[i]=sc.nextDouble();
			y[i]=sc.nextDouble();
		}
		for(int i=0;i<n;i++){
			for(int j=0;j<n;j++){
				if(i==j)continue;
				if(Math.abs(x[i]-x[j])<=10&&Math.abs(y[i]-y[j])<=10){
					if((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j])<=100){
						uni.setUnion(i, j);	
					}
				}
			}
		}
		double max=0;
		for(int i=0;i<n;i++){
			for(int j=0;j<n;j++){
				if(i==j)continue;
				if(uni.root(i)==uni.root(j)){

					max=Math.max(max,(x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
				}
			}
		}
		if(n==0){
			System.out.println(1);
			return;
		}else{
			System.out.println(Math.sqrt(max)+2);
		}


	}
	static class UnionFind{
		int[] f;
		UnionFind(int size){
			f=new int[size];
			Arrays.fill(f, -1);
		}
		boolean setUnion(int x,int y){
			x=root(x);
			y=root(y);
			if(x!=y){
				if(f[x]>f[y]){
					int d=x;
					x=y;
					y=d;
				}
				f[x]+=f[y];
				f[y]=x;
			}
			return x!=y;
		}
		int root(int x){
			return f[x]<0?x:root(f[x]);
		}
	}
}