HTML/CSS - challenge - ↘zigzag-square Online Editor and JavaScript Compiler

html

<!DOCTYPE html>
<html>
<!--
challenge: https://www.sololearn.com/Discuss/743087/
proposed by Vitaliy Kondrat'ev.
made by ysraelcon.
-->
    <head>
        <title>SouthEast-ZigZag-Square</title>
    </head>
    <body>
    
    <p>Input a number n:</p>
    <input type=number id=inn><br>
    <input type=button value="Make SouthEast-ZigZag-Square NxN:" onclick=mS()><br>
    <pre id=pr></pre>
    
    
    <script>
    
     var hlm;
        
     function mS(){
         
         var n=parseInt(inn.value);
         
         var ln=n*n;

css

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