Problem:
Score : 100 points

Problem Statement

It is known that the area of a regular dodecagon inscribed in a circle of radius a is 3a^2.

Given an integer r, find the area of a regular dodecagon inscribed in a circle of radius r.

Constraints

1 \leq r \leq 100

r is an integer.

Input

Input is given from Standard Input in the following format:

r

Output

Print an integer representing the area of the regular dodecagon.

Sample Input 1

4

Sample Output 1

48

The area of the regular dodecagon is 3 \times 4^2 = 48.

Sample Input 2

15

Sample Output 2

675

Sample Input 3

80

Sample Output 3

19200

Solution in Go (1.6) (judge verdict: Wrong Answer)

package main

import (
	"fmt"
)

type ll int64


func main() {

	var N int
	fmt.Scan(&N)


	a := make([]int, N+1)
	ans := 0
	ans_slice := make([]int,N+1)


	for i := 0 ; i < N ;i++ {
		//1 origin
		fmt.Scan(&a[i+1])
	}

	ans_flag := 0
	for i:= N; i > 0 ; i--  {//Nから1まで

		k:= i
		j := 1
		ans_flag = 0

		for k <= N  {
			ans_flag += a[k]
			j++
			k = i * j
		}


		if ans_flag % 2 != 0 {//2で割り切れない
			ans++
			ans_slice[i] = 1
		}

	}






	fmt.Println(ans)
	for i:=1;i <=N ;i++  {
		if ans_slice[i] == 1 {
			fmt.Print(i)
			//fmt.Print(" ")
		}
	}
	//fmt.Println("")

}