Answer 1

You can make it a macro

https://code.sololearn.com/czY6aZcqfxqv/?ref=app

Answer 2

// Arsenic answer is relevant to get your code more readable, but you doesn't need to define a macro:

#include <iostream>
using namespace std;

int main()
{

unsigned long long n = 1234567890\
0987654321ULL;
cout<<n;

return 0;
}

// works as well ;P

Answer 3

https://code.sololearn.com/W4h8G3ZkcCIG/?ref=app