<p>Given an integer <code>num</code>, return <em>a string of its <strong>base 7</strong> representation</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> num = 100
<strong>Output:</strong> "202"
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> num = -7
<strong>Output:</strong> "-10"
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>-10<sup>7</sup> &lt;= num &lt;= 10<sup>7</sup></code></li>
</ul>

class Solution:
    def convertToBase7(self, num: int) -> str:
        neg = num < 0
        num = abs(num)
        ans = ''
        while num:
            num, rem = num // 7, num % 7
            ans += str(rem)
        return ('-' + ans[::-1] if neg else ans[::-1]) or '0'
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