CF121A.Lucky Sum
普及/提高-
通过率:0%
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题目描述
Petya loves lucky numbers. Everybody knows that lucky numbers are positive integers whose decimal representation contains only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.
Let next(x) be the minimum lucky number which is larger than or equals x . Petya is interested what is the value of the expression next(l)+next(l+1)+...+next(r−1)+next(r) . Help him solve this problem.
输入格式
The single line contains two integers l and r ( 1<=l<=r<=109 ) — the left and right interval limits.
输出格式
In the single line print the only number — the sum next(l)+next(l+1)+...+next(r−1)+next(r) .
Please do not use the %lld specificator to read or write 64-bit integers in C++. It is preferred to use the cin, cout streams or the %I64d specificator.
输入输出样例
输入#1
2 7
输出#1
33
输入#2
7 7
输出#2
7
说明/提示
In the first sample: next(2)+next(3)+next(4)+next(5)+next(6)+next(7)=4+4+4+7+7+7=33
In the second sample: next(7)=7