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

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

Output

Output the least super lucky number that is more than or equal to $*n*$.

Please, do not use the %lld specificator to read or write 64-bit integers in C++. It is preferred to use the cin, cout streams or the %I64d specificator.