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*.

The only line contains a positive integer *n* (1 ≤ *n* ≤ 10^{9}). This number doesn't have leading zeroes.

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