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+<title>Day 11 - Advent of Code 2018</title>
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+Oh, hello! Funny seeing you here.
+
+I appreciate your enthusiasm, but you aren't going to find much down here.
+There certainly aren't clues to any of the puzzles. The best surprises don't
+even appear in the source until you unlock them for real.
+
+Please be careful with automated requests; I'm not Google, and I can only take
+so much traffic. Please be considerate so that everyone gets to play.
+
+If you're curious about how Advent of Code works, it's running on some custom
+Perl code. Other than a few integrations (auth, analytics, ads, social media),
+I built the whole thing myself, including the design, animations, prose, and
+all of the puzzles.
+
+The puzzles are most of the work; the easiest ones take 3-4 hours each, but the
+harder ones take 6-8 hours, and a few even longer than that. A lot of effort
+went into building this thing - I hope you're enjoying playing it as much as I
+enjoyed making it for you!
+
+If you'd like to hang out, I'm @ericwastl on Twitter.
+
+- Eric Wastl
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+<body>
+<header><div><h1 class="title-global"><a href="/">Advent of Code</a></h1><nav><ul><li><a href="/2018/about">[About]</a></li><li><a href="/2018/events">[Events]</a></li><li><a href="https://teespring.com/adventofcode" target="_blank">[Shop]</a></li><li><a href="/2018/settings">[Settings]</a></li><li><a href="/2018/auth/logout">[Log Out]</a></li></ul></nav><div class="user">Neil Smith <a href="/2018/support" class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a> <span class="star-count">22*</span></div></div><div><h1 class="title-event"> <span class="title-event-wrap">{year=></span><a href="/2018">2018</a><span class="title-event-wrap">}</span></h1><nav><ul><li><a href="/2018">[Calendar]</a></li><li><a href="/2018/support">[AoC++]</a></li><li><a href="/2018/sponsors">[Sponsors]</a></li><li><a href="/2018/leaderboard">[Leaderboard]</a></li><li><a href="/2018/stats">[Stats]</a></li></ul></nav></div></header>
+
+<div id="sidebar">
+<div id="sponsor"><div class="quiet">Our <a href="/2018/sponsors">sponsors</a> help make Advent of Code possible:</div><div class="sponsor"><a href="https://clubhouse.io/?utm_source=spon&utm_medium=ch&utm_campaign=aoc2018" target="_blank" onclick="if(ga)ga('send','event','sponsor','click',this.href);" rel="noopener">Clubhouse</a> - The first project management platform for software development that brings everyone on every team together to build better products. AoC participants get two free months by signing up at r.clbh.se/mze9q9P Also, we're hiring!</div></div>
+</div><!--/sidebar-->
+
+<main>
+<article class="day-desc"><h2>--- Day 11: Chronal Charge ---</h2><p>You watch the Elves and their sleigh fade into the distance as they head toward the North Pole.</p>
+<p>Actually, you're the one fading. The <span title="wheeeeeeeeeeeeeeeeee">falling sensation</span> returns.</p>
+<p>The low fuel warning light is illuminated on your wrist-mounted device. Tapping it once causes it to project a hologram of the situation: a <em>300x300</em> grid of fuel cells and their current power levels, some negative. You're not sure what negative power means in the context of time travel, but it can't be good.</p>
+<p>Each fuel cell has a coordinate ranging <em>from 1 to 300</em> in both the X (horizontal) and Y (vertical) direction. In <code>X,Y</code> notation, the top-left cell is <code>1,1</code>, and the top-right cell is <code>300,1</code>.</p>
+<p>The interface lets you select <em>any 3x3 square</em> of fuel cells. To increase your chances of getting to your destination, you decide to choose the 3x3 square with the <em>largest total power</em>.</p>
+<p>The power level in a given fuel cell can be found through the following process:</p>
+<ul>
+<li>Find the fuel cell's <em>rack ID</em>, which is its <em>X coordinate plus 10</em>.</li>
+<li>Begin with a power level of the <em>rack ID</em> times the <em>Y coordinate</em>.</li>
+<li>Increase the power level by the value of the <em>grid serial number</em> (your puzzle input).</li>
+<li>Set the power level to itself multiplied by the <em>rack ID</em>.</li>
+<li>Keep only the <em>hundreds digit</em> of the power level (so <code>12<em>3</em>45</code> becomes <code>3</code>; numbers with no hundreds digit become <code>0</code>).</li>
+<li><em>Subtract 5</em> from the power level.</li>
+</ul>
+<p>For example, to find the power level of the fuel cell at <code>3,5</code> in a grid with serial number <code>8</code>:</p>
+<ul>
+<li>The rack ID is <code>3 + 10 = <em>13</em></code>.</li>
+<li>The power level starts at <code>13 * 5 = <em>65</em></code>.</li>
+<li>Adding the serial number produces <code>65 + 8 = <em>73</em></code>.</li>
+<li>Multiplying by the rack ID produces <code>73 * 13 = <em>949</em></code>.</li>
+<li>The hundreds digit of <code><em>9</em>49</code> is <code><em>9</em></code>.</li>
+<li>Subtracting 5 produces <code>9 - 5 = <em>4</em></code>.</li>
+</ul>
+<p>So, the power level of this fuel cell is <code><em>4</em></code>.</p>
+<p>Here are some more example power levels:</p>
+<ul>
+<li>Fuel cell at <code>122,79</code>, grid serial number <code>57</code>: power level <code>-5</code>.</li>
+<li>Fuel cell at <code>217,196</code>, grid serial number <code>39</code>: power level <code>0</code>.</li>
+<li>Fuel cell at <code>101,153</code>, grid serial number <code>71</code>: power level <code>4</code>.</li>
+</ul>
+<p>Your goal is to find the 3x3 square which has the largest total power. The square must be entirely within the 300x300 grid. Identify this square using the <code>X,Y</code> coordinate of its <em>top-left fuel cell</em>. For example:</p>
+<p>For grid serial number <code>18</code>, the largest total 3x3 square has a top-left corner of <code><em>33,45</em></code> (with a total power of <code>29</code>); these fuel cells appear in the middle of this 5x5 region:</p>
+<pre><code>-2 -4 4 4 4
+-4 <em> 4 4 4 </em>-5
+ 4 <em> 3 3 4 </em>-4
+ 1 <em> 1 2 4 </em>-3
+-1 0 2 -5 -2
+</code></pre>
+<p>For grid serial number <code>42</code>, the largest 3x3 square's top-left is <code><em>21,61</em></code> (with a total power of <code>30</code>); they are in the middle of this region:</p>
+<pre><code>-3 4 2 2 2
+-4 <em> 4 3 3 </em> 4
+-5 <em> 3 3 4 </em>-4
+ 4 <em> 3 3 4 </em>-3
+ 3 3 3 -5 -1
+</code></pre>
+<p><em>What is the <code>X,Y</code> coordinate of the top-left fuel cell of the 3x3 square with the largest total power?</em></p>
+</article>
+<p>Your puzzle answer was <code>21,34</code>.</p><article class="day-desc"><h2 id="part2">--- Part Two ---</h2><p>You discover a dial on the side of the device; it seems to let you select a square of <em>any size</em>, not just 3x3. Sizes from 1x1 to 300x300 are supported.</p>
+<p>Realizing this, you now must find the <em>square of any size with the largest total power</em>. Identify this square by including its size as a third parameter after the top-left coordinate: a 9x9 square with a top-left corner of <code>3,5</code> is identified as <code>3,5,9</code>.</p>
+<p>For example:</p>
+<ul>
+<li>For grid serial number <code>18</code>, the largest total square (with a total power of <code>113</code>) is 16x16 and has a top-left corner of <code>90,269</code>, so its identifier is <code><em>90,269,16</em></code>.</li>
+<li>For grid serial number <code>42</code>, the largest total square (with a total power of <code>119</code>) is 12x12 and has a top-left corner of <code>232,251</code>, so its identifier is <code><em>232,251,12</em></code>.</li>
+</ul>
+<p><em>What is the <code>X,Y,size</code> identifier of the square with the largest total power?</em></p>
+</article>
+<p>Your puzzle answer was <code>90,244,16</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
+<p>At this point, you should <a href="/2018">return to your advent calendar</a> and try another puzzle.</p>
+<p>Your puzzle input was <code class="puzzle-input">5719</code>.</p>
+<p>You can also <span class="share">[Share<span class="share-content">on
+ <a href="https://twitter.com/intent/tweet?text=I%27ve+completed+%22Chronal+Charge%22+%2D+Day+11+%2D+Advent+of+Code+2018&url=https%3A%2F%2Fadventofcode%2Ecom%2F2018%2Fday%2F11&related=ericwastl&hashtags=AdventOfCode" target="_blank">Twitter</a>
+ <a href="http://www.reddit.com/submit?url=https%3A%2F%2Fadventofcode%2Ecom%2F2018%2Fday%2F11&title=I%27ve+completed+%22Chronal+Charge%22+%2D+Day+11+%2D+Advent+of+Code+2018" target="_blank">Reddit</a
+></span>]</span> this puzzle.</p>
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