Codeforces Round #270 A. Design Tutorial: Learn from Math【数论/埃氏筛法】

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

One way to create a task is to learn from math. You can generate some random math statement or modify some theorems to get something new and build a new task from that.

For example, there is a statement called the "Goldbach's conjecture". It says: "each even number no less than four can be expressed as the sum of two primes". Let's modify it. How about a statement like that: "each integer no less than 12 can be expressed as the sum of two composite numbers." Not like the Goldbach's conjecture, I can prove this theorem.

You are given an integer n no less than 12, express it as a sum of two composite numbers.

Input

The only line contains an integer n (12 ≤ n ≤ 106).

Output

Output two composite integers x and y (1 < x, y < n) such that x + y = n. If there are multiple solutions, you can output any of them.

Sample test(s)

input

12

output

4 8

input

15

output

6 9

input

23

output

8 15

input

1000000

output

500000 500000

Note

In the first example, 12 = 4 + 8 and both 4, 8 are composite numbers. You can output "6 6" or "8 4" as well.

In the second example, 15 = 6 + 9. Note that you can't output "1 14" because 1 is not a composite number.

【注意】：埃氏筛法筛素数时，注意开头i*2非i*i(数字大爆int)

【代码】：

#include<bits/stdc++.h>
using namespace std;
int prime[];
void get_prime()
{
    prime[]=prime[]=;//0,1非素数
    for(int i=;i<=;i++)
    {
        if(prime[i]==)
            for(int j=i*;j<=;j+=i)
               prime[j]=;
    }
}
int main()
{
    int n;
    get_prime();
    cin>>n;
    for(int i=;i<=n;i++)
        if( prime[i]&& prime[n-i] )
        {
            printf("%d %d\n",i,n-i);
            return ;
        }
    return ;
}

筛法