#include <iostream>
using namespace std;
struct Node
{
    int data;
    struct Node* left;
    struct Node* right;
};
struct Node* addNode(int data)
{
    struct Node* node = new Node;
    node->data = data;
    node->left = NULL;
    node->right = NULL;
    return (node);
};
int result = 0;
int sumOfEvenNodes(struct Node* root)
{
    if(root == NULL)
        return result;
    else
    {
        if(root->data%2==0)
        {
            result += root->data;
        }
    }
    sumOfEvenNodes(root->left);
    sumOfEvenNodes(root->right);
}
int main()
{
    struct Node* root = addNode(1);
    root->right = addNode(2);
    root->right->left = addNode(-3);
    root->right->right = addNode(-4);
    root->left = addNode(3);
    root->left->left = addNode(4);
    root->left->right = addNode(-5);
    root->left->right->right = addNode(6);
    root->left->left->left = addNode(-1);
    root->left->left->right = addNode(-2);
    cout<<sumOfEvenNodes(root);
    return 0;
}