A prime number is a natural number greater than 1 and has exactly 2 divisors which are 1 and the number itself.
You are given a prime number n, find any 2 prime numbers a and b such that a+b=n or state that no such pair of primes exists.
Input
The input contains a single prime number n(2≤n≤107).
Output
If there doesn’t exist any 2 primes such that their summation is equal to n then print -1, otherwise print the 2 primes on a single line separated by a space.
Examples
Input
5
Output
2 3
Input
11
Output
-1
思路：使用了最新學到的打表法
#include<bits/stdc++.h>
using namespace std;
const int maxx=1e7+10;
int a[maxx];
int main()
{
std::ios::sync_with_stdio(false);
int flag=0;
int n;
cin>>n;
a[1]=1;
for(int i=2; i<=n; i++)
{
if(!a[i])
{
for(int j=i+i; j<n; j+=i)
a[j]=1;
}
}
for(int i=2; i<n; i++)
{
if(!a[i])
{
if(!a[n-i])
{
flag=1;
cout<<i<<" "<<n-i<<endl;
break;
}
}
}
if(flag==0)
cout<<-1<<endl;
return 0;
}