package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func configure(scanner *bufio.Scanner) {
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
}
func getNextString(scanner *bufio.Scanner) string {
	scanned := scanner.Scan()
	if !scanned {
		panic("scan failed")
	}
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	extra := 0
	if os.Getenv("I") == "IronMan" {
		fp, _ = os.Open(os.Getenv("END_GAME"))
		extra = 100
	}
	scanner := bufio.NewScanner(fp)
	configure(scanner)
	writer := bufio.NewWriter(wfp)
	defer func() {
		r := recover()
		if r != nil {
			fmt.Fprintln(writer, r)
		}
		writer.Flush()
	}()
	solve(scanner, writer)
	for i := 0; i < extra; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	n := 5
	tickets := make([]int64, n)
	for i := 0; i < n; i++ {
		tickets[i] = getNextInt64(scanner)
	}
	var l, r int64
	l = -1
	r = int64(1e16)
	for l+1 < r {
		m := (l + r) >> 1
		if enable(m, tickets) {
			l = m
			continue
		}
		r = m
	}
	fmt.Fprintln(writer, l)
}

func enable(m int64, tickets []int64) bool {
	n := 5
	tt := make([]int64, n)
	for i := 0; i < n; i++ {
		tt[i] = min(m, tickets[i]) - m
	}
	tt[0] += m
	tt[1] += m
	for i := 0; i < n*2; i++ {
		if tt[i%n] > 0 {
			tt[(i+2)%n] += tt[i%n]
			tt[i%n] = 0
		}
	}
	for i := 0; i < n; i++ {
		if tt[i] < 0 {
			return false
		}
	}
	return true
}

func min(a, b int64) int64 {
	if a < b {
		return a
	}
	return b
}