Prime generator got TLE

hi im really frustated about my code since i already optimize my code and still got tle (T^T) here my code

click here

or

    #include<iostream>
#include<stdio.h>
#include<set>
#include<math.h>
using namespace std;
bool isprime(int n)
{

          for(int x=3;x<=int(sqrt(n));x+=2)if(n%x==0)return 0;
          return 1;
}
    int main()

{
    set<int> prime;
    prime.insert(2);prime.insert(3);prime.insert(5);
    prime.insert(7);
    for(int x=9;x<=32000;x+=2)
    {
             if(isprime(x))prime.insert(x);       
    }
    set<int>::iterator it;
   int t;
   scanf("%d",&t);
   while(t--)
   {
   int a,b;
   scanf("%d %d",&a,&b);
   if(b>32000){
               if(!(a&1))a++;
   for(int x=a;x<=b;x+=2)
   {
           bool cek=1;
           for(it=prime.begin();it!=prime.end();it++)
           {

                 if(*it>int(sqrt(x)))break;
                 if(x%*it==0){cek=0;break;}                                          
           }        
           if(cek)printf("%d\n",x);
   }          
   }
   else
   {

             for(it=prime.begin();*it<=b && it!=prime.end();it++)
           {

                 if(*it>=a && *it<=b )   printf("%d\n",*it);

           }


   }
}
}