Jim has 100 cards.
There is a whole number from 1 to 100 on each card.
No cards have the same number.
Jim puts a star on every card that has a multiple of 3 on it.
He puts a circle on every card that has a multiple of 7 on it.
What numbers are on the cards that have both a star and a circle on them?
The final line of your answer must list only these numbers.