Q:

How to count by three from the number given by the user?

I have to create a program using a for loop that will count by 3 from the given number from the user 20 times. So far this is what i have.
#include <iostream>
using namespace std;

int main(){
  int num, newNum, add;
  cout << "Enter a number: ";
  cin >> num;

  for(int count = 0; count < 20; count++){
    for(int sum = 0; sum <= count; sum++){
      newNum = num * (count +1);
    }
    cout << num << " ";
  }
}

I have no idea where to go from here. I know that i would have to put the number given into a variable like i do with num and i know i would somehow have to store the new number in another variable like i do with newNum. Any help would be appreciated! Also this is what the output should look like in case i did not explain it good enough.
Enter a number: 3
3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48, 51, 54, 57, 60.

And bonus points if you can have the last number end with a period instead of a comma :)

A:

This should work:
int main(){
   int num, currentNum, add, newNum;
   std::cout << "Enter a number: ";
   std::cin >> num;
   std::cout << num
   for(int count = 0; count < 20; count++){
         num += 3;
         std::cout << ", " << num;
   }
   std::cout << " ." << std::endl;
}

Also try to not use using namespace std. It clutters the namespace.

