class Solution:
    def getDecimalValue(self, head: ListNode) -> int:
        if not head:
            return 0
        temp=[]
        while(head):
            temp.append(head.val)
            head=head.next
        l=len(temp)
        ans=0
        for i in range(l):
            ans+=(temp[~i]*(2**i))
        return ans