| Time Limit: 1000MS | Memory Limit: 65535KB | 64bit IO Format: %lld & %llu |
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
Hint
Source
第七届ACM趣味程序设计竞赛第四场（正式赛）
这一个估计就是最水的的了，找到规律之后判断一下就好
#include<string.h>
#include<stdlib.h>
#include<math.h>
#include<iostream>
#include<algorithm>
using namespace std;
int main()
{
long long n;
while(scanf("%lld",&n)!=EOF)
{
if(n<7)
printf("-1
");
else
printf("7
");
}
return 0;
}