Lucky Interval

4000ms

524288K

Description:

Petya loves lucky numbers. We all know that lucky numbers are the positive integers whose decimal representations contain only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.

One day Petya came across an interval of numbers [a, a + l - 1]. Let F(x) be the number of lucky digits of number x. Find the minimum b (a < b) such, that F(a) = F(b), F(a + 1) = F(b + 1), ..., F(a + l - 1) = F(b + l - 1).

Input:

The single line contains two integers a and l (1 ≤ a, l ≤ 10⁹) — the interval's first number and the interval's length correspondingly.

Output:

On the single line print number b — the answer to the problem.

Sample Input:

7 4

Sample Output:

Sample Input:

4 7

Sample Output:

Note:

Consider that [a, b] denotes an interval of integers; this interval includes the boundaries. That is, $\text{[math]}$

Informação

Provedor Codeforces

Código CF109E