finding the least bigger number from the tree

i need to find the node in this BST tree which is the least bigger the the other nodes.

i know i need to use preorder traversal here.
how to solve it??

Code:

---


node * nextNode(node  * tree, int number)
{
        int left,right;
        node* temp
  if (!tree)
  {
    return NULL;
  }
  if (tree->left)
  {
          temp=nextNode(tree->left,number);
      if (number<temp->value)
          {
                  left=temp->value;
          }
  }

  if (tree->value>number)
  {
    return tree;
  }
  else
  return NULL;
 
  if (tree->right)
  {
          temp=nextNode(tree->right,number);
      if (number<temp->value)
          {
                  right=temp->value;
          }
  }


}

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