<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 s1, string s2) {
    
        if(s1.length()==s2.length())
        {if(s1==s2) return s1;
        else
            return "";
        }
        if(s1.length()<s2.length())
            {
               string tmp=s1;
                s1=s2;
                s2=tmp;
            }     
        string tmp="";
        int i=0;
        string res="";
        while(i<s1.length())
        {
            tmp.push_back(s1[i]);
            string curr=tmp;
            
            bool flag=false;
            if(s1.length()%curr.length()!=0||s2.length()%curr.length()!=0)    
                {
                    i++;
                    continue;
                }
            while(curr.length()<s1.length())
            {
                if(curr==s2)
                    flag=true;
                curr+=tmp;
               
            }
            if(curr==s1&&(flag||curr==s2))
                res=tmp;
            i++;
           
        }
        return res;


        
    }
};
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