# node implementation

class Node:
    def __init__(self):
        self.children = []
        self.score = None
        self.inner = None
    def calculate(self):
        if self.children == []:
            return self.score
        total = 0
        items = 0
        for i in self.children:
            score = i.calculate()
            if score != None:
                items += 1
                total += score