package main

import . "fmt"
import . "sort"

func main() {
	var n int
	Scan(&n)
	a:=make([]int,n)
	for i:=range a {
		Scan(&a[i])
	}
	Ints(a)
	Println(float32(a[n/2]+a[n/2+1-n%2])/2)
}