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)

#pragma region include
#include "bits/stdc++.h"
#define ALL(obj) (obj).begin(),(obj).end()
#define RALL(obj) (obj).rbegin(),(obj).rend()
#define REP(i, n) for(int i = 0; i < (int)(n); i++)
#define REPR(i, n) for(int i = (int)(n); i >= 0; i--)
#define FOR(i,n,m) for(int i = (int)(n); i < int(m); i++)
using namespace std;
typedef long long ll;
typedef pair<int, int> PII;
const int MOD = 1e9 + 7;
const int INF = 1e9;
const ll LLINF = 4e18;
void input() {}
template<typename... R> void input(int& f, R&... r) { scanf("%d", &f); input(r...); }
template<typename... R> void input(double& f, R&... r) { scanf("%lf", &f); input(r...); }
template<typename... R> void input(ll& f, R&... r) { scanf("%lld", &f); input(r...); }
template<typename... R> void input(char& f, R&... r) { scanf("%c", &f); input(r...); }
template<typename T, typename... R> void input(vector<T>& f, R&... r) { REP(i, f.size())input(f[i]); input(r...); }
#pragma endregion

int main() {
    int r; input(r);
    cout << 3 * r * r << endl;
    getchar(); getchar();
}