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<vector>
#include<iostream>
#include<algorithm>
#include<functional>
#include<string>
#include<limits.h>
#include<cmath>
#include<queue>
#include<map>
#define rep(i,n) for (int i=0; i<n; i++)
using namespace std;
typedef long long ll;

ll gcd(ll a,ll b){
  ll r;
  while ((r=a%b)){a=b;b=r;}
  return b;
}

int main(){

  int r; cin >> r;
  cout << 3 * r * r;

  return 0;
}