Are you sure? It looks correct to me. If the number is not multiple of 3 or 5, you must output the number. That's what is he doing. He prints output at the en

Are you sure? It looks correct to me. If the number is not multiple of 3 or 5, you must output the number. That's what is he doing. He prints output at the end of each iteration, setting it to empty string at the beginning.