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,n) for(long long int i = 0; i < n; i++)
#define _rep(i,m,n) for(long long int i = m; i < n; i++)
#define print(n) std::cout << n << std::endl
#define _print(n) std::cout << n
using namespace std;
typedef long long ll;
const int N = 1000000;
const ll mod = 1000000007;
using Graph = vector<vector<int>>;

int main(){
   int r; cin >> r;
   print(r * r * 3);
}