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 C (GCC 5.4.1) (judge verdict: Accepted)

/*
 * main.c
 *
 *  Created on: 2019/07/07
 *      Author: family
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

typedef unsigned long long int uint64_t;
typedef long long int int64my_t;

//qsort(a, 3, sizeof(int), sort_inc);
int sort_inc(const void *a, const void *b)
{
    return (*(int*)a - *(int*)b);
}
int sort_dec(const void* a, const void* b)
{
    return (*(int*)b - *(int*)a);
}

int main()
{
	int r = 0;
	scanf("%d", &r);
	printf("%d\n", 3*r*r);
    return 0;
}