# Definition for a  binary tree node
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    # @param A : root node of tree
    # @return the root node in the tree

    def getpreorder(self,x,l):
        if x == None:
            return l
        l.append(x.val)
        l = self.getpreorder(x.left,l)
        l = self.getpreorder(x.right,l)
        return l


    def flatten(self, A):
        l = []
        r = self.getpreorder(A,l)
        root = TreeNode(l[0])
        prev = root
        for i in range(1,len(l)):
            x = TreeNode(l[i])
            prev.right = x
            prev = x

        return root