44. Uncle Wang and Uncle Li from the exploration team are conducting surveys on a desolate mountain, and they are expected to work for another 7 days before they can come down the mountain. However, they only have 3 bottles of drinking water left. Under normal circumstances, each person needs to drink at least one bottle of water per day. After contacting the command center, the command center immediately sent Uncle Ding to deliver water. If it takes 1 day to go up the mountain and 1 day to come down, then Uncle Ding needs to bring at least $\qquad$ bottles of water up the mountain.
answer: 15