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 <bits/stdc++.h>
using namespace std;

#define rep(i, n) for (int (i) = 0; (i) < (n); (i)++)
#define rng(i, a, b) for (int (i) = (a); (i) < (b); (i)++)
#define rbf(i, v) for (auto& (i) : (v))
#define all(x) (x).begin(),(x).end()
#define cAll(x) (x).cbegin(),(x).cend()
#define COUT(x) cout << x << endl
//#define int long long

template<typename T> constexpr auto square(T x) { return (x) * (x); }

typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef vector<PII> VP;

const int MOD = 1000000007;
const int INF = INT_MAX;

signed main()
{
	int r;
	cin >> r;

	int ans = 3 * r * r;

	COUT(ans);

	return 0;
}