T了三个点，求大佬优化代码！

#include <iostream>
#define re register
using namespace std;
bool zs(int x)
{
	for (re int i=2;i*i<=x;i++)
	   if (x%i==0)
	     return 0;
	return 1;
}
bool hw(int x)
{
    int y=x,n=0;
    while (y!=0)
    {
        n=n*10+y%10;
        y/=10;
    } 
    if (n==x)
	  return 1;
    else
      return 0;
}
int main()
{
	int a,b;
	std::ios::sync_with_stdio(false);
	cin>>a>>b;
	if (a%2==0)
	{
		for (re int i=a+1;i<=b;i+=2)
	    {
	    	if (i>5&&i%5==0)
	    	  continue;
		    if (zs(i)&&hw(i))
		      cout<<i<<endl;
	    }
	}
	else
	{
		for (re int i=a;i<=b;i+=2)
	    {
	    	if (i>5&&i%5==0)
	    	  continue;
		    if (zs(i)&&hw(i))
		      cout<<i<<endl;  
	    }
	}
	return 0;
}