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>
#define rep(i, end) for (long long int i=0; i<end; i++)
#define repp(i, begin, end) for (long long int i=begin; i<end; i+)
#define srt(x) sort((x).begin(), (x).end());
#define rsrt(x) sort((x).rbegin(), (x).rend());
#define deb(x) cout<<#x<<" = "<<(x)<<" (L"<<__LINE__<<")"<<endl;
using namespace std;
using ll = long long int;
using vi = vector<int>;
using vll = vector<long long int>;
using vllvll = vector<vll>;
using vs = vector<string>;
ll sm(vll x) {ll sum=0; rep(i, x.size()) sum+=x[i]; return sum;}
void vdeb(string s, vll x) {cout<<s<<" = { "; rep(i, x.size()) cout<<x[i]<<' '; cout <<'}'<<endl;}
//=======================================================================================================

int main()
{
    ll r;
    cin >> r;
    cout << 3 * r * r << endl;
    return 0;
}