<p>Given <code>head</code> which is a reference node to a singly-linked list. The value of each node in the linked list is either <code>0</code> or <code>1</code>. The linked list holds the binary representation of a number.</p>

<p>Return the <em>decimal value</em> of the number in the linked list.</p>

<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/12/05/graph-1.png" style="width: 426px; height: 108px;" />
<pre>
<strong>Input:</strong> head = [1,0,1]
<strong>Output:</strong> 5
<strong>Explanation:</strong> (101) in base 2 = (5) in base 10
</pre>

<p><strong>Example 2:</strong></p>

<pre>
<strong>Input:</strong> head = [0]
<strong>Output:</strong> 0
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The Linked List is not empty.</li>
	<li>Number of nodes&nbsp;will not exceed <code>30</code>.</li>
	<li>Each node&#39;s value is either&nbsp;<code>0</code> or <code>1</code>.</li>
</ul>