title: getting an issue when adding strings?
body: <p>I am having issues with the second to last 'elif' statement, I am getting the concatenation error with str and integers-&gt; any explanation to why this is? My understanding is that I am adding a string &quot;R&quot; to the empty string next_row.</p>
  <p>Specifically the error is &quot;can only concatenate str (not &quot;int&quot;) to str&quot;</p>
  <pre><code>  def triangle(row):
       next_row = ''
  
       for i in row:
           if i == 'G' and (i + 1) == 'B':
               next_row += 'R'
  
           elif i == 'G' and (i + 1) == 'R':
               next_row += 'B'
  
           elif i == 'R' and (i + 1) == 'B':
               next_row += 'G'
  
           elif i == 'R' and (i + 1) == 'G':
               next_row += 'B'
  
           elif i == 'B' and (i + 1) == 'G':
               next_row += 'R'
  
           elif i == 'B' and (i + 1) == 'R':
               next_row += 'G'
  
       print(type(next_row))
       return None
  
   triangle(&quot;BRGGBRG&quot;)
  </code></pre>