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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <utility>
#include <string>
#include <stack>
#include <regex>
#include <numeric>
#include <queue>
#include <set>

#define REP(i, n) for (int i = 0; i < n; i++)
#define ALL(v) (v).begin(), (v).end()

using namespace std;

typedef long long ll;

int main(int argc, char const *argv[])
{
  ll r;
  cin >> r;
  cout << 3 * r * r << endl;
  return 0;
}