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 <algorithm>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstring>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#define rs(a, b) ((a) >> (b))
#define ls(a, b) ((a) << (b))
#define gcd __gcd
#define lcm(a, b) ((a * b) / gcd(a, b))
#define pq priority_queue
#define um unordered_map
#define us unordered_set
#define lb lower_bound
#define ub upper_bound
#define F first
#define B begin()
#define E end()
#define ln length()
#define sz size()
#define S second
#define em empty()
#define nani(x) cerr << #x << " is " << x << endl;
#define ch(x) (x - 'a' + 1)
#define mp make_pair
#define pb push_back
#define loop(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
#define scan(x, n) loop(i, 0, n) cin >> x[i];
#define adde(g, u, v) g[u].pb(v), g[v].pb(u);
#define addew(g, u, v, w) g[u].pb({ v, w }), g[v].pb({ u, w });
#define print(x, n) loop(i, 0, n) cout << x[i] << " ";
#define fast ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define inf 10000000000
#define mod 1000000007

using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<long> vl;
typedef vector<vi> vvi;
typedef pair<int, int> ii;
typedef pair<long, long> pll;
typedef vector<ii> vii;
typedef vector<pll> vll;
typedef um<int, int> umii;
typedef um<char, int> umci;
typedef map<char, int> mci;
typedef map<int, int> mii;

int main()
{
    fast;
    //freopen("input.txt", "r", stdin);
    int r;
    cin >> r;
    cout << 3 * r * r;
    return 0;
}