<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:
    string gcdOfStrings(string str1, string str2) {
        int xx = 0, y = 0;
        int n = str1.size(), m = str2.size();
        if (n > m) {
            for (int i = m - 1; i >= 0; i--) {
               xx=0;
                string pref = str2.substr(0, i + 1);
                if (n % pref.size() == 0) {
               xx=0;
                    int jj = n / pref.size();
                    string kk = "";
                    while (jj--) {
                        kk += pref;
                    }
                    if (kk == str1)
                        xx = 1;
                    
                }
                if (m % pref.size() == 0) {

                    int jj = m / pref.size();
                    string kk = "";
                    while (jj--) {
                        kk += pref;
                    }
                    if (kk == str2 && xx)
                        return pref;
                }
            }

        } else {
            for (int i = n - 1; i >= 0; i--) {
                 y=0;
                string pref = str1.substr(0, i + 1);
                if (m % pref.size() == 0) {
                 //  y=0;
                    int jj = m / pref.size();
                    string kk = "";
                    while (jj--) {
                        kk += pref;
                    }
                    if (kk == str2)
                        y = 1;
                }
                if (n % pref.size() == 0) {

                    int jj = n / pref.size();
                    string kk = "";
                    while (jj--) {
                        kk += pref;
                    }
                    if (kk == str1 && y)
                        return pref;
                }
            }
        }

        return "";
    }
};
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