typedef struct tree_node_s {
  int value;
  struct tree_node_s* left;
  struct tree_node_s* right;
} tree_node_t;

tree_node_t *second_max_value(tree_node_t *node) {
  tree_node_t* previous = NULL;
  tree_node_t* current = node;

  while (current->right != NULL) {
    previous = current;
    current = current->right;
  }

  if (current->left != NULL) {
    current = current->left;
    while (current->right != NULL) {
      current = current->right;
    }

    return current;
  } else {
    return previous;
  }
}