/**
knakul853
 */
class Solution {
public:
    pair<int,int>p;

    int kthSmallest(TreeNode* root, int k) {

        p.first = 0;
        p.second = 0;

         dfs(root, k);
        return p.second;

    }

    void dfs(TreeNode* root, int k)
    {
        if(!root) return;

         dfs(root->left, k);
        if(p.first < k)
        {
            p.first++;
            p.second = root->val;
        }

        if(p.first < k)
        {
            dfs(root->right, k);
        }
    }
};