Day1_3LetandConst.js

const PI = Math.PI; //Declare a constant variable, , and assign it the value Math.PI.
let r = readLine(); //Read a number, , denoting the radius of a circle from stdin.
var squaredNumber = (r * r); //this is to get a square of number R 
console.log(PI * squaredNumber); // Print the area of the circle 
console.log( 2 * PI * r); // Print the perimeter of the circle