#include <bits/stdc++.h>
using namespace std;
void isprime(unsigned long long a,unsigned long long b){
if(a<=2 && b>=2) cout<<2<<endl;if(a<=3 && b>=3) cout<<3<<endl;
for(unsigned long long i=a;i<=b;i++){
if(((i-1)%6 ==0 && i-1!=0 )|| (i+1) %6 ==0){
cout<<i<<endl;
}
}
cout<<endl;
}
int main() {
unsigned long long t;
cin>>t;
unsigned long long a,b;
for(unsigned long long i=0;i<t;i++){
cin>>a>>b;
isprime(a,b);
}
return 0;
}
I have used divisibility by 6n+1 or 6n-1 to check prime or not.
Thanks.