If the depth of a tree is smaller than 5, then this tree can be represented by a list of three-digits integers. For each integer in this list: The hundreds digit represents the depth D of this node, 1 <= D <= 4. The tens digit represents the position P of this node in the level it belongs to, 1 <= P <= 8. The position is the same as that in a full binary tree. The units digit represents the value V of this node, 0 <= V <= 9. Given a list of ascending three-digits integers representing a binary tree with the depth smaller than 5, you need to return the sum of all paths from the root towards the leaves. It's guaranteed that the given list represents a valid connected binary tree. Example 1: Input: [113, 215, 221] Output: 12 Explanation: The tree that the list represents is: 3 / \ 5 1 The path sum is (3 + 5) + (3 + 1) = 12. Example 2: Input: [113, 221] Output: 4 Explanation: The tree that the list represents is: 3 \ 1 The path sum is (3 + 1) = 4.