The area of an equilateral triangle is ¼(√3a2) where "a" represents a side of the triangle. You are provided with the side "a". Find the area of the equilateral triangle.

The area of an equilateral triangle is ¼(√3a²) where "a" represents a side of the triangle. You are provided with the side "a". Find the area of the equilateral triangle.

Input Description:
The side of an equilateral triangle is provided as the input.

Output Description:
Find the area of the equilateral triangle and print the answer up to 2 decimal places after rounding off.

Sample Input :
20

Sample Output :
173.21

const readline = require('readline');
 const inp = readline.createInterface({
  input: process.stdin
 });
 const userInput = [];
 inp.on("line", (data) => {
 userInput.push(data);
 });
 inp.on("close", () => {
 var data = userInput[0].split(" ");
 var a = parseInt(data[0]);
 b= Math.sqrt(3);
c=(1/4)*b*a*a;
console.log(c.toFixed(2));
});