package main

import (
	"fmt"
	"sort"
)

func main() {
	S := make([]int, 6)
	for i := range S {
		fmt.Scan(&S[i])
	}
	sort.Ints(S)
	sum := 0
	for i := 1; i <= 4; i++ {
		sum += S[i]
	}
	fmt.Printf("%.2f\n", float64(sum)/4)
}