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)

//↓template↓

#include "bits/stdc++.h"
using namespace std;
#define Would
#define you
#define all(n)  n.begin(),n.end()
#define rall(n) n.rbegin(),n.rend()
typedef long long ll;
//typedef complex<double>P;
const ll INF = 1e18;
const ll MOD = 1e9 + 7;
const double EPS = 1e-10;
const double pi = acos(-1);//3.1415926535897932384626433832795028...
const ll SIZE = 1 << 17;
int dx[] = { 1,0,-1,0 }, dy[] = { 0,1,0,-1 }, alp[30];
ll fac[200005], finv[200005], inv[200005];
vector<ll>dij;
struct edge { ll to, cost; };
vector<vector<edge> >G;

ll mod_pow(ll a, ll b) {
	ll res = 1, mul = a;
	for (int i = 0; i < 31; ++i) {
		if (b >> i & 1) {
			res *= mul;
			res %= MOD;
		}
		mul = (mul * mul) % MOD;
	}
	return res;
}

void addedge(int from, int to, int cost) {
	G[from].push_back({ to,cost });
	G[to].push_back({ from,cost });
}

template<typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }

template<typename T, typename... Ts>
auto make_v(size_t a, Ts... ts) {
	return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

template<typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type
fill_v(T &t, const V &v) { t = v; }

template<typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type
fill_v(T &t, const V &v) {
	for (auto &e : t) fill_v(e, v);
}

template<typename T>
void outp(vector<T>v) {
	for (int i = 0; i < v.size(); ++i) {
		cout << v[i];
		if (i != v.size() - 1) { cout << " "; }
	}
}

double add(double a, double b) {
	if (abs(a + b) < EPS*(abs(a) + abs(b))) { return 0; }
	return a + b;
}


//↑template↑

int main() {
	int n;
	cin >> n;
	cout << 3 * n*n << endl;
}