John thinks 4 and 7 are lucky digits, and all other digits are not lucky. A lucky number is a number that contains only lucky digits in decimal notation.
Some numbers can be represented as a sum of only lucky numbers. Given an int n, return a int whose elements sum to exactly n. Each element of the int must be a lucky number. If there are multiple solutions, only consider those that contain the minimum possible number of elements, and return the one among those that comes earliest lexicographically. A int a1 comes before a int a2 lexicographically if a1 contains a smaller number at the first position where they differ. If n cannot be represented as a sum of lucky numbers, return an empty int instead.