A tree rooted at node 0 is given as follows: The number of nodes is nodes; The value of the i-th node is value[i]; The parent of the i-th node is parent[i]. Remove every subtree whose sum of values of nodes is zero. After doing so, return the number of nodes remaining in the tree. Example 1: Input: nodes = 7, parent = [-1,0,0,1,2,2,2], value = [1,-2,4,0,-2,-1,-1] Output: 2 Example 2: Input: nodes = 7, parent = [-1,0,0,1,2,2,2], value = [1,-2,4,0,-2,-1,-2] Output: 6 Example 3: Input: nodes = 5, parent = [-1,0,1,0,0], value = [-672,441,18,728,378] Output: 5 Example 4: Input: nodes = 5, parent = [-1,0,0,1,1], value = [-686,-842,616,-739,-746] Output: 5 Constraints: 1 <= nodes <= 10^4 parent.length == nodes 0 <= parent[i] <= nodes - 1 parent[0] == -1 which indicates that 0 is the root. value.length == nodes -10^5 <= value[i] <= 10^5 The given input is guaranteed to represent a valid tree.