Read input numbers separated by spaces

By default, cin reads from the input discarding any spaces. So, all you have to do is to use a do while loop to read the input more than one time:

do {
   cout<<"Enter a number, or numbers separated by a space, between 1 and 1000."<<endl;
   cin >> num;

   // reset your variables

   // your function stuff (calculations)
}
while (true); // or some condition