Given a Binary Tree. Return **1** if, for every node **X** in the tree other than the leaves, its value is equal to the sum of its left subtree's value and its right subtree's value. Else return **0**.

An empty tree is also a Sum Tree as the sum of an empty tree can be considered to be 0. A leaf node is also considered a Sum Tree.

**Example 1:**

Input:3 / \ 1 2Output:1Explanation:The sum of left subtree and right subtree is 1 + 2 = 3, which is the value of the root node. Therefore,the given binary tree is asum tree.

**Example 2:**

Input:10 / \ 20 30 / \ 10 10Output:0Explanation:The given tree is not a sum tree. For the root node, sum of elements in left subtree is 40 and sum of elements in right subtree is 30. Root element = 10 which is not equal to 30+40.

**Your Task: **

You don't need to read input or print anything. Complete the function **isSumTree() **which takes **root **node as input parameter and returns true if the tree is a SumTree else it returns false.

**Expected Time Complexity: **O(N)

**Expected Auxiliary Space:** O(Height of the Tree)

**Constraints:**

1 ≤ number of nodes ≤ 10^{4}