Description: Petya loves lucky numbers. Everybody knows that positive integers are lucky if their decimal representation doesn't contain digits other than 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not. Lucky number is super lucky if it's decimal representation contains equal amount of digits 4 and 7. For example, numbers 47, 7744, 474477 are super lucky and 4, 744, 467 are not. One day Petya came across a positive integer n. Help him to find the least super lucky number which is not less than n. Input Format: The only line contains a positive integer n (1 ≤ n ≤ 10100000). This number doesn't have leading zeroes. Output Format: Output the least super lucky number that is more than or equal to n. Note: None