# Definition for singly-linked list.

# class ListNode:

#     def __init__(self, x):

#         self.val = x

#         self.next = None

class Solution:

    def getDecimalValue(self, head: ListNode) -> int:

        if not head:

            return 0

        l = []

        cur = head

        while cur:

            l.append(str(cur.val))

            cur = cur.next

        res = "".join(l)

        res = int(res,2)

        return res