<p>For two strings <code>s</code> and <code>t</code>, we say &quot;<code>t</code> divides <code>s</code>&quot; if and only if <code>s = t + t + t + ... + t + t</code> (i.e., <code>t</code> is concatenated with itself one or more times).</p>

<p>Given two strings <code>str1</code> and <code>str2</code>, return <em>the largest string </em><code>x</code><em> such that </em><code>x</code><em> divides both </em><code>str1</code><em> and </em><code>str2</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> str1 = &quot;ABCABC&quot;, str2 = &quot;ABC&quot;
<strong>Output:</strong> &quot;ABC&quot;
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> str1 = &quot;ABABAB&quot;, str2 = &quot;ABAB&quot;
<strong>Output:</strong> &quot;AB&quot;
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> str1 = &quot;LEET&quot;, str2 = &quot;CODE&quot;
<strong>Output:</strong> &quot;&quot;
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= str1.length, str2.length &lt;= 1000</code></li>
	<li><code>str1</code> and <code>str2</code> consist of English uppercase letters.</li>
</ul>

class Solution {
public:
    bool isDiv(int l, string str1, string str2) {

        if (((str2.length()) % l) || ((str2.length()) % l))
            return false;

        string a1 = "";
        string a2 = "";

        for (int i = 0; i < ((str1.length()) / l); i++) {
            a1 += str1.substr(0, l);
        }

        for (int i = 0; i < ((str2.length()) / l); i++) {
            a2 += str1.substr(0, l);
        }
        return ((a1 == str1) && (a2 == str2));
    }
    string gcdOfStrings(string str1, string str2) {
        int len1 = str1.length();
        int len2 = str2.length();

        for (int l = (min(len1, len2)); l > 0; l--) {
            // cout << l;
            if (isDiv(l, str1, str2))
                return (str1.substr(0, l));
        }

        return "";
    }
};
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