package main

type TreeNode struct {
	Val   int
	Left  *TreeNode
	Right *TreeNode
}

func main() {

}
func kthSmallest(root *TreeNode, k int) int {
	var helper func(root *TreeNode) []int
	helper = func(root *TreeNode) []int {
		if root == nil {
			return []int{}
		}
		tmp := make([]int, 0)
		tmp = append(tmp, helper(root.Left)...)
		tmp = append(tmp, root.Val)
		tmp = append(tmp, helper(root.Right)...)

		return tmp
	}
	res := helper(root)
	return res[k-1]
}