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.
Sample Input
8
Sample Output
7
#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstdio>
#include<vector>
#include<cstring>
#include<string>
using namespace std;
typedef long long LL;
const int maxn = 1e4 + 5;
const int base = 1e9 + 7;
const int low(int x){ return x&-x; }
int T, m;
int f[maxn];
LL n;
int main(){
//scanf("%d", &T);
while (~scanf("%lld", &n))
{
if (n >= 7) printf("7\n"); else printf("-1\n");
}
return 0;
}