There is one Koyuki. One minute later, she splits into two Koyukis; after another minute, each of those Koyukis split in two and become four Koyukis. If she continues to divide in this way, one Koyuki will fill up a room in 30 minutes. If Yuuka trapped Koyuki in a room as soon as she saw her divide, how many minutes would it take for the room to be entirely filled up?