求优化方案

#include<iostream>
#include<math.h>
using namespace std;
bool x[290005];
int main()
{
    int n;
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= sqrt(i); j++)
        {
            if (i % j == 0)
            {
                x[i] = true;
            }
        }
    }
    for (int i = 3; i <= n; i+=2)
    {
        if (x[i] != false)
        {
        	if (x[i + 2] != 0)
	        {
	               cout << i << ' ' << i + 2 << endl;
	        }
        }
    }
    return 0;
}