package main

import (
	"fmt"
	"sort"
)

var luckyNumbers []int64

func generateLuckyNumbers(current int64) {
	if current > 10000000000 {
		return
	}
	if current > 0 {
		luckyNumbers = append(luckyNumbers, current)
	}
	generateLuckyNumbers(current*10 + 4)
	generateLuckyNumbers(current*10 + 7)
}

func main() {
	var l, r int64
	fmt.Scan(&l, &r)

	generateLuckyNumbers(0)
	sort.Slice(luckyNumbers, func(i, j int) bool {
		return luckyNumbers[i] < luckyNumbers[j]
	})

	var totalSum int64
	currentL := l

	for currentL <= r {
		idx := sort.Search(len(luckyNumbers), func(i int) bool {
			return luckyNumbers[i] >= currentL
		})
		
		lucky := luckyNumbers[idx]
		
		end := lucky
		if r < lucky {
			end = r
		}
		
		count := end - currentL + 1
		totalSum += count * lucky
		
		currentL = end + 1
	}

	fmt.Println(totalSum)
}