E. Lucky Intervaltime limit per test4 secondsmemory limit per test512 megabytesinputstandard inputoutputstandard outputPetya 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).InputThe single line contains two integers a and l (1 ≤ a, l ≤ 109) — the interval's first number and the interval's length correspondingly.OutputOn the single line print number b — the answer to the problem.ExamplesInput7 4Output17Input4 7Output14NoteConsider that [a, b] denotes an interval of integers; this interval includes the boundaries. That is, 
Input7 4
Output17
['brute force', 'math', '*2700']