# [C# (Visual C# Interactive Compiler)], 47 bytes

<!-- language-all: lang-cs -->

<pre><code>s=&gt;!s.Where((c,i)=&gt;c!=$"{s}&#1;"[i+1-i%2*2]).Any()
</code></pre>

[Try it online!][TIO-jz0qqowb]

[C# (Visual C# Interactive Compiler)]: http://www.mono-project.com/docs/about-mono/releases/5.0.0/#csc
[TIO-jz0qqowb]: https://tio.run/##ncsxCsIwFABQXHuKJCgk2hbsWlNwcXIsdBCHJv21n5ak5LeDiGePiDdweduzlFnCeFmdPdES0D1S4/1U9TqSrjjlzQABpLQpKl1ZrrfiRe@NuOHhmOGu2Bd3lZ/dU6pYJkkTcIErOpC9FHU9DIhEjP3sOu/X1ZhpAmCMaJ4B2nYcORdKlX/eb40f "C# (Visual C# Interactive Compiler) – Try It Online"