Water Collected after Rain

You are given an array where each element represents the height of the terrain at that index. Calculate the total amount of water that can be trapped between the terrain after it rains. The input consists of one line, which contains space-separated integers representing the heights. The output should be a single integer representing the total water trapped. Example Input: 5 0 1 0 2 1 0 1 3 2 1 2 1 Example Output: 6