package main

import (
	"fmt"
	"math"
)

func norm(x, y int) int {
	return x*x + y*y
}

var res []int

func dfs(u int, used []bool, x, y []int) {
	if used[u] {
		return
	}
	res = append(res, u)
	used[u] = true
	for i, _ := range x {
		if norm(x[i]-x[u], y[i]-y[u]) <= 100 {
			dfs(i, used, x, y)
		}
	}
}
func main() {
	var n int
	fmt.Scan(&n)
	x := make([]int, n)
	y := make([]int, n)
	for i, _ := range x {
		fmt.Scan(&x[i], &y[i])
	}
	used := make([]bool, n)
	ans := 1.0
	for i, v := range used {
		if !v {
			res = make([]int, 0)
			dfs(i, used, x, y)
			for _, u := range res {
				for _, v := range res {
					d := 2 + math.Sqrt(float64(norm(x[u]-x[v], y[u]-y[v])))
					if ans < d {
						ans = d
					}
				}
			}
		}
	}
	fmt.Printf("%.12f\n", ans)
}