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<a class="header-anchor-link" href="#%E5%95%8F%E9%A1%8C" aria-hidden="true"></a> 問題</h1>
<p>Prove that if seven distinct numbers are selected from {1, 2,..., 11}, then some two of these numbers sum to 12.</p>
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<a class="header-anchor-link" href="#%E8%A8%BC%E6%98%8E" aria-hidden="true"></a> 証明</h2>
<p>Since seven numbers are selected, the Pigeonhole Principle guarantees that two of them are selected from one of the six sets <code>{1, 11}, {2, 10}, {3, 9}, {4, 8}, {5, 7}, {6}</code>. These two numbers sum to 12.</p>
<ul>
<li><a href="https://www.math.uvic.ca/faculty/gmacgill/guide/pigeonhole.pdf" target="_blank" rel="nofollow noopener noreferrer">https://www.math.uvic.ca/faculty/gmacgill/guide/pigeonhole.pdf</a></li>
</ul>


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