<p>You are given the string <code>croakOfFrogs</code>, which represents a combination of the string <code>&quot;croak&quot;</code> from different frogs, that is, multiple frogs can croak at the same time, so multiple <code>&quot;croak&quot;</code> are mixed.</p>

<p><em>Return the minimum number of </em>different<em> frogs to finish all the croaks in the given string.</em></p>

<p>A valid <code>&quot;croak&quot;</code> means a frog is printing five letters <code>&#39;c&#39;</code>, <code>&#39;r&#39;</code>, <code>&#39;o&#39;</code>, <code>&#39;a&#39;</code>, and <code>&#39;k&#39;</code> <strong>sequentially</strong>. The frogs have to print all five letters to finish a croak. If the given string is not a combination of a valid <code>&quot;croak&quot;</code> return <code>-1</code>.</p>

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

<pre>
<strong>Input:</strong> croakOfFrogs = &quot;croakcroak&quot;
<strong>Output:</strong> 1 
<strong>Explanation:</strong> One frog yelling &quot;croak<strong>&quot;</strong> twice.
</pre>

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

<pre>
<strong>Input:</strong> croakOfFrogs = &quot;crcoakroak&quot;
<strong>Output:</strong> 2 
<strong>Explanation:</strong> The minimum number of frogs is two. 
The first frog could yell &quot;<strong>cr</strong>c<strong>oak</strong>roak&quot;.
The second frog could yell later &quot;cr<strong>c</strong>oak<strong>roak</strong>&quot;.
</pre>

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

<pre>
<strong>Input:</strong> croakOfFrogs = &quot;croakcrook&quot;
<strong>Output:</strong> -1
<strong>Explanation:</strong> The given string is an invalid combination of &quot;croak<strong>&quot;</strong> from different frogs.
</pre>

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

<ul>
	<li><code>1 &lt;= croakOfFrogs.length &lt;= 10<sup>5</sup></code></li>
	<li><code>croakOfFrogs</code> is either <code>&#39;c&#39;</code>, <code>&#39;r&#39;</code>, <code>&#39;o&#39;</code>, <code>&#39;a&#39;</code>, or <code>&#39;k&#39;</code>.</li>
</ul>

class Solution {
public:
    int minNumberOfFrogs(string cf) {
        int ans=0;
        int n=cf.length();
        int c=0,r=0,o=0,a=0;
        int nc=0,nr=0,no=0,na=0,nk=0;
        for(int i=0;i<n;i++)
        {
            if(cf[i]=='c')
            {
                c++;
                if(ans>0)
                {
                    ans--;
                }
                nc++;
            }
            else if(cf[i]=='r')
            {
                if(c>0)
                {
                    c--;
                    r++;
                    nr++;
                }
            }
            else if(cf[i]=='o')
            {
                if(r>0)
                {
                    r--;
                    o++;
                    no++;
                }
            }
            else if(cf[i]=='a')
            {
                if(o>0)
                {
                    o--;
                    a++;
                    na++;
                }
            }
            else
            {
                if(a>0)
                {
                    a--;
                    ans++;
                    nk++;
                }
            }
        }
        if(n==5*nc && (nc==nr) && (nr==no) && (no==na) && (na==nk))
        {
            return ans;
        }
        return -1;
    }
};
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