Given head which is a reference node to a singly-linked list. The value of each node in the linked list is either 0 or 1. The linked list holds the binary representation of a number. Return the decimal value of the number in the linked list. Example 1: Input: head = [1,0,1] Output: 5 Explanation: (101) in base 2 = (5) in base 10 Example 2: Input: head = [0] Output: 0 Example 3: Input: head = [1] Output: 1 Example 4: Input: head = [1,0,0,1,0,0,1,1,1,0,0,0,0,0,0] Output: 18880 Example 5: Input: head = [0,0] Output: 0 Constraints: The Linked List is not empty. Number of nodes will not exceed 30. Each node's value is either 0 or 1.