daily/286easy/problem.html


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<h1 id="description">Description</h1>
<p>Nearly everyone is familiar with the factorial operator in math. 5! yields 120 because factorial means &quot;multiply successive terms where each are one less than the previous&quot;:</p>
<pre><code>5! -&gt; 5 * 4 * 3 * 2 * 1 -&gt; 120</code></pre>
<p>Simple enough.</p>
<p>Now let's reverse it. Could you write a function that tells us that &quot;120&quot; is &quot;5!&quot;?</p>
<p>Hint: The strategy is pretty straightforward, just divide the term by successively larger terms until you get to &quot;1&quot; as the resultant:</p>
<pre><code>120 -&gt; 120/2 -&gt; 60/3 -&gt; 20/4 -&gt; 5/5 -&gt; 1 =&gt; 5!</code></pre>
<h1 id="sample-input">Sample Input</h1>
<p>You'll be given a single integer, one per line. Examples:</p>
<pre><code>120
150</code></pre>
<h1 id="sample-output">Sample Output</h1>
<p>Your program should report what each number is as a factorial, or &quot;NONE&quot; if it's not legitimately a factorial. Examples:</p>
<pre><code>120 = 5!
150   NONE</code></pre>
<h1 id="challenge-input">Challenge Input</h1>
<pre><code>3628800
479001600
6
18</code></pre>
<h1 id="challenge-output">Challenge Output</h1>
<pre><code>3628800 = 10!
479001600 = 12!
6 = 3!
18  NONE</code></pre>