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<p>The <strong>count-and-say</strong> sequence is a sequence of digit strings defined by the recursive formula:</p>
<ul>
<li><code>countAndSay(1) = "1"</code></li>
<li><code>countAndSay(n)</code> is the way you would "say" the digit string from <code>countAndSay(n-1)</code>, which is then converted into a different digit string.</li>
</ul>
<p>To determine how you "say" a digit string, split it into the <strong>minimal</strong> number of substrings such that each substring contains exactly <strong>one</strong> unique digit. Then for each substring, say the number of digits, then say the digit. Finally, concatenate every said digit.</p>
<p>For example, the saying and conversion for digit string <code>"3322251"</code>:</p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/10/23/countandsay.jpg" style="width: 581px; height: 172px;" />
<p>Given a positive integer <code>n</code>, return <em>the </em><code>n<sup>th</sup></code><em> term of the <strong>count-and-say</strong> sequence</em>.</p>
<p> </p>
<p><strong class="example">Example 1:</strong></p>
<pre>
<strong>Input:</strong> n = 1
<strong>Output:</strong> "1"
<strong>Explanation:</strong> This is the base case.
</pre>
<p><strong class="example">Example 2:</strong></p>
<pre>
<strong>Input:</strong> n = 4
<strong>Output:</strong> "1211"
<strong>Explanation:</strong>
countAndSay(1) = "1"
countAndSay(2) = say "1" = one 1 = "11"
countAndSay(3) = say "11" = two 1's = "21"
countAndSay(4) = say "21" = one 2 + one 1 = "12" + "11" = "1211"
</pre>
<p> </p>
<p><strong>Constraints:</strong></p>
<ul>
<li><code>1 <= n <= 30</code></li>
</ul>
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