S</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">&#39;</span><span class="nv">N</span><span class="o">&#39;</span><span class="w"> </span><span class="ow">or</span><span class="w"> </span><span class="o">&#39;</span><span class="nv">n</span><span class="o">&#39;</span><span class="w">   </span><span class="nv">x</span><span class="w"> </span><span class="o">:=</span><span class="w"> </span><span class="nv">A</span><span class="o">*</span><span class="nv">x</spa