Migrated from Lutece 1272 Final Pan's prime numbers

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Description

Final Pan likes prime numbers very much.

One day, he want to find the super prime numbers.A prime numbers $n$($n$>4) is a super prime number only if $n$-4 and $n$+4 are both prime numbers,too.

Your task is really easy：Give $N$，find the maximum super prime number $n$ that $n$<=$N$.

Input

Only one integer $N.( 4<N<10^{12} )$

Output

If there is no such interger $n$，print'$-1$',otherwise print $n$.

Samples

8

7

Resources

第七届ACM趣味程序设计竞赛第四场（正式赛）