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: Accepted)

package main

import (
	"fmt"
	"math"
)

func main() {
	var r int
	fmt.Scan(&r)
	fmt.Println(3 * r * r)
}

var dy = []int{0, 1, 0, -1}
var dx = []int{1, 0, -1, 0}
var inf = int(1e9)

func pow(a, b int) int {
	return int(math.Pow(float64(a), float64(b)))
}

func lcm(a, b int) int {
	return a * b / gcd(a, b)
}
func gcd(a, b int) int {
	if a < b {
		a, b = b, a
	}
	for b != 0 {
		a, b = b, a%b
	}
	return a
}
func max(a ...int) int {
	r := a[0]
	for i := 0; i < len(a); i++ {
		if r < a[i] {
			r = a[i]
		}
	}
	return r
}
func min(a ...int) int {
	r := a[0]
	for i := 0; i < len(a); i++ {
		if r > a[i] {
			r = a[i]
		}
	}
	return r
}
func sum(a []int) (r int) {
	for i := range a {
		r += a[i]
	}
	return r
}
func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

type Pair struct {
	a, b int
}

type pairs []Pair

func (p pairs) Len() int {
	return len(p)
}
func (p pairs) Swap(i, j int) {
	p[i], p[j] = p[j], p[i]
}

func (p pairs) Less(i, j int) bool {
	if p[i].a == p[j].a {
		return p[i].b < p[j].b
	}
	return p[i].a < p[j].a
}

// bug bug
// var nextReader func() []byte
//
// func init() {
// 	nextReader = newScanner()
// 	log.SetFlags(log.Lshortfile)
// }
//
// func newScanner() func() []byte {
// 	r := bufio.NewScanner(os.Stdin)
// 	r.Split(bufio.ScanWords)
// 	return func() []byte {
// 		r.Scan()
// 		return r.Bytes()
// 	}
// }
// func nextBytes() []byte {
// 	return nextReader()
// }
//
// func nextString() string {
// 	return string(nextReader())
// }
// func nextInt64() int64 {
// 	v, _ := strconv.ParseInt(string(nextReader()), 10, 64)
// 	return v
// }
// func nextInt() int {
// 	v, _ := strconv.Atoi(string(nextReader()))
// 	return v
// }
// func nextInts(n int) []int {
// 	r := make([]int, n)
// 	for i := 0; i < n; i++ {
// 		r[i] = nextInt()
// 	}
// 	return r
// }
// func nextFloat64() float64 {
// 	f, _ := strconv.ParseFloat(string(nextReader()), 64)
// 	return f
// }