Prime number#242

Prime number

1 second

64 megabytes

Easy

A natural number $X$ is called a derivative of a natural number $N$ if $X$ either coincides with $N$ or can be obtained by deleting some digits from the decimal representation of $N$ . For example, the derivatives of the number $1024$ are $1$ , $2$ , $4$ , $10$ , $12$ , $14$ , $24$ , $102$ , $104$ , $124$ , and $1024$ .

Given a natural number $N$ , determine the largest prime number $P$ which is a derivative of $N$ . If none of the derivatives of $N$ is prime, take $P = 0$ P = 0. A natural number $P$ is called prime if $P \neq = 1$ P \neq 1 and $P$ has no divisors other than $1$ and $P$ .

Input

The only line of input contains the number $N$ ( $0 < N < 1 0^{9}$ 0 < N < 10^9).

Output

The program should output the number $P$ .

Examples

Example 1

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P = 0

P \neq = 1

0 < N < 1 0^{9}