Write a function f1 that takes the root of a binary tree as a parameter and returns the sum of the nodes which are the right child of another node. The root of the tree is not a child of any node....

Write a function f1 that takes the root of a binary tree as a parameter and returns the sum of the nodes which are the right child of another node. The root of the tree is not a child of any node. Consider the following class definitions while writing your code. Using c++ language.

class Node {
public:
int key;
Node* left;
Node* right;
};