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  16 Oh, hello!  Funny seeing you here.
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  18 I appreciate your enthusiasm, but you aren't going to find much down here.
  19 There certainly aren't clues to any of the puzzles.  The best surprises don't
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  22 Please be careful with automated requests; I'm not a massive company, and I can
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  25 If you're curious about how Advent of Code works, it's running on some custom
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  27 I built the whole thing myself, including the design, animations, prose, and
  28 all of the puzzles.
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  30 The puzzles are most of the work; preparing a new calendar and a new set of
  31 puzzles each year takes all of my free time for 4-5 months. A lot of effort
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  35 If you'd like to hang out, I'm @ericwastl on Twitter.
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  37 - Eric Wastl
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  90 <header><div><h1 class="title-global"><a href="/">Advent of Code</a></h1><nav><ul><li><a href="/2019/about">[About]</a></li><li><a href="/2019/events">[Events]</a></li><li><a href="https://teespring.com/adventofcode-2019" target="_blank">[Shop]</a></li><li><a href="/2019/settings">[Settings]</a></li><li><a href="/2019/auth/logout">[Log Out]</a></li></ul></nav><div class="user">Neil Smith <a href="/2019/support" class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a> <span class="star-count">28*</span></div></div><div><h1 class="title-event">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="title-event-wrap">/^</span><a href="/2019">2019</a><span class="title-event-wrap">$/</span></h1><nav><ul><li><a href="/2019">[Calendar]</a></li><li><a href="/2019/support">[AoC++]</a></li><li><a href="/2019/sponsors">[Sponsors]</a></li><li><a href="/2019/leaderboard">[Leaderboard]</a></li><li><a href="/2019/stats">[Stats]</a></li></ul></nav></div></header>
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  98 <article class="day-desc"><h2>--- Day 14: Space Stoichiometry ---</h2><p>As you approach the rings of Saturn, your ship's <em>low fuel</em> indicator turns on.  There isn't any fuel here, but the rings have plenty of raw material.  Perhaps your ship's <span title="Yes, the acronym is intentional.">Inter-Stellar Refinery Union</span> brand <em>nanofactory</em> can turn these raw materials into fuel.</p>
  99 <p>You ask the nanofactory to produce a list of the <em>reactions</em> it can perform that are relevant to this process (your puzzle input). Every reaction turns some quantities of specific <em>input chemicals</em> into some quantity of an <em>output chemical</em>. Almost every <em>chemical</em> is produced by exactly one reaction; the only exception, <code>ORE</code>, is the raw material input to the entire process and is not produced by a reaction.</p>
 100 <p>You just need to know how much <code><em>ORE</em></code> you'll need to collect before you can produce one unit of <code><em>FUEL</em></code>.</p>
 101 <p>Each reaction gives specific quantities for its inputs and output; reactions cannot be partially run, so only whole integer multiples of these quantities can be used.  (It's okay to have leftover chemicals when you're done, though.) For example, the reaction <code>1 A, 2 B, 3 C =&gt; 2 D</code> means that exactly 2 units of chemical <code>D</code> can be produced by consuming exactly 1 <code>A</code>, 2 <code>B</code> and 3 <code>C</code>.  You can run the full reaction as many times as necessary; for example, you could produce 10 <code>D</code> by consuming 5 <code>A</code>, 10 <code>B</code>, and 15 <code>C</code>.</p>
 102 <p>Suppose your nanofactory produces the following list of reactions:</p>
 103 <pre><code>10 ORE =&gt; 10 A
 104 1 ORE =&gt; 1 B
 105 7 A, 1 B =&gt; 1 C
 106 7 A, 1 C =&gt; 1 D
 107 7 A, 1 D =&gt; 1 E
 108 7 A, 1 E =&gt; 1 FUEL
 109 </code></pre>
 110 <p>The first two reactions use only <code>ORE</code> as inputs; they indicate that you can produce as much of chemical <code>A</code> as you want (in increments of 10 units, each 10 costing 10 <code>ORE</code>) and as much of chemical <code>B</code> as you want (each costing 1 <code>ORE</code>).  To produce 1 <code>FUEL</code>, a total of <em>31</em> <code>ORE</code> is required: 1 <code>ORE</code> to produce 1 <code>B</code>, then 30 more <code>ORE</code> to produce the 7 + 7 + 7 + 7 = 28 <code>A</code> (with 2 extra <code>A</code> wasted) required in the reactions to convert the <code>B</code> into <code>C</code>, <code>C</code> into <code>D</code>, <code>D</code> into <code>E</code>, and finally <code>E</code> into <code>FUEL</code>. (30 <code>A</code> is produced because its reaction requires that it is created in increments of 10.)</p>
 111 <p>Or, suppose you have the following list of reactions:</p>
 112 <pre><code>9 ORE =&gt; 2 A
 113 8 ORE =&gt; 3 B
 114 7 ORE =&gt; 5 C
 115 3 A, 4 B =&gt; 1 AB
 116 5 B, 7 C =&gt; 1 BC
 117 4 C, 1 A =&gt; 1 CA
 118 2 AB, 3 BC, 4 CA =&gt; 1 FUEL
 119 </code></pre>
 120 <p>The above list of reactions requires <em>165</em> <code>ORE</code> to produce 1 <code>FUEL</code>:</p>
 121 <ul>
 122 <li>Consume 45 <code>ORE</code> to produce 10 <code>A</code>.</li>
 123 <li>Consume 64 <code>ORE</code> to produce 24 <code>B</code>.</li>
 124 <li>Consume 56 <code>ORE</code> to produce 40 <code>C</code>.</li>
 125 <li>Consume 6 <code>A</code>, 8 <code>B</code> to produce 2 <code>AB</code>.</li>
 126 <li>Consume 15 <code>B</code>, 21 <code>C</code> to produce 3 <code>BC</code>.</li>
 127 <li>Consume 16 <code>C</code>, 4 <code>A</code> to produce 4 <code>CA</code>.</li>
 128 <li>Consume 2 <code>AB</code>, 3 <code>BC</code>, 4 <code>CA</code> to produce 1 <code>FUEL</code>.</li>
 129 </ul>
 130 <p>Here are some larger examples:</p>
 131 <ul>
 132 <li><p><em>13312</em> <code>ORE</code> for 1 <code>FUEL</code>:</p>
 133 <pre><code>157 ORE =&gt; 5 NZVS
 134 165 ORE =&gt; 6 DCFZ
 135 44 XJWVT, 5 KHKGT, 1 QDVJ, 29 NZVS, 9 GPVTF, 48 HKGWZ =&gt; 1 FUEL
 136 12 HKGWZ, 1 GPVTF, 8 PSHF =&gt; 9 QDVJ
 137 179 ORE =&gt; 7 PSHF
 138 177 ORE =&gt; 5 HKGWZ
 139 7 DCFZ, 7 PSHF =&gt; 2 XJWVT
 140 165 ORE =&gt; 2 GPVTF
 141 3 DCFZ, 7 NZVS, 5 HKGWZ, 10 PSHF =&gt; 8 KHKGT
 142 </code></pre></li>
 143 <li><p><em>180697</em> <code>ORE</code> for 1 <code>FUEL</code>:</p>
 144 <pre><code>2 VPVL, 7 FWMGM, 2 CXFTF, 11 MNCFX =&gt; 1 STKFG
 145 17 NVRVD, 3 JNWZP =&gt; 8 VPVL
 146 53 STKFG, 6 MNCFX, 46 VJHF, 81 HVMC, 68 CXFTF, 25 GNMV =&gt; 1 FUEL
 147 22 VJHF, 37 MNCFX =&gt; 5 FWMGM
 148 139 ORE =&gt; 4 NVRVD
 149 144 ORE =&gt; 7 JNWZP
 150 5 MNCFX, 7 RFSQX, 2 FWMGM, 2 VPVL, 19 CXFTF =&gt; 3 HVMC
 151 5 VJHF, 7 MNCFX, 9 VPVL, 37 CXFTF =&gt; 6 GNMV
 152 145 ORE =&gt; 6 MNCFX
 153 1 NVRVD =&gt; 8 CXFTF
 154 1 VJHF, 6 MNCFX =&gt; 4 RFSQX
 155 176 ORE =&gt; 6 VJHF
 156 </code></pre></li>
 157 <li><p><em>2210736</em> <code>ORE</code> for 1 <code>FUEL</code>:</p>
 158 <pre><code>171 ORE => 8 CNZTR
 159 7 ZLQW, 3 BMBT, 9 XCVML, 26 XMNCP, 1 WPTQ, 2 MZWV, 1 RJRHP => 4 PLWSL
 160 114 ORE => 4 BHXH
 161 14 VRPVC => 6 BMBT
 162 6 BHXH, 18 KTJDG, 12 WPTQ, 7 PLWSL, 31 FHTLT, 37 ZDVW => 1 FUEL
 163 6 WPTQ, 2 BMBT, 8 ZLQW, 18 KTJDG, 1 XMNCP, 6 MZWV, 1 RJRHP => 6 FHTLT
 164 15 XDBXC, 2 LTCX, 1 VRPVC => 6 ZLQW
 165 13 WPTQ, 10 LTCX, 3 RJRHP, 14 XMNCP, 2 MZWV, 1 ZLQW => 1 ZDVW
 166 5 BMBT => 4 WPTQ
 167 189 ORE => 9 KTJDG
 168 1 MZWV, 17 XDBXC, 3 XCVML => 2 XMNCP
 169 12 VRPVC, 27 CNZTR => 2 XDBXC
 170 15 KTJDG, 12 BHXH => 5 XCVML
 171 3 BHXH, 2 VRPVC => 7 MZWV
 172 121 ORE => 7 VRPVC
 173 7 XCVML => 6 RJRHP
 174 5 BHXH, 4 VRPVC => 5 LTCX
 175 </code></pre></li>
 176 </ul>
 177 <p>Given the list of reactions in your puzzle input, <em>what is the minimum amount of <code>ORE</code> required to produce exactly 1 <code>FUEL</code>?</em></p>
 178 </article>
 179 <p>Your puzzle answer was <code>598038</code>.</p><article class="day-desc"><h2 id="part2">--- Part Two ---</h2><p>After collecting <code>ORE</code> for a while, you check your cargo hold: <em>1 trillion</em> (<em>1000000000000</em>) units of <code>ORE</code>.</p>
 180 <p><em>With that much ore</em>, given the examples above:</p>
 181 <ul>
 182 <li>The 13312 <code>ORE</code>-per-<code>FUEL</code> example could produce <em>82892753</em> <code>FUEL</code>.</li>
 183 <li>The 180697 <code>ORE</code>-per-<code>FUEL</code> example could produce <em>5586022</em> <code>FUEL</code>.</li>
 184 <li>The 2210736 <code>ORE</code>-per-<code>FUEL</code> example could produce <em>460664</em> <code>FUEL</code>.</li>
 185 </ul>
 186 <p>Given 1 trillion <code>ORE</code>, <em>what is the maximum amount of <code>FUEL</code> you can produce?</em></p>
 187 </article>
 188 <p>Your puzzle answer was <code>2269325</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
 189 <p>At this point, you should <a href="/2019">return to your Advent calendar</a> and try another puzzle.</p>
 190 <p>If you still want to see it, you can <a href="14/input" target="_blank">get your puzzle input</a>.</p>
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