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++ (GCC 9.2.1) (judge verdict: Accepted)

// #define _GLIBCXX_DEBUG
// #pragma GCC optimize("Ofast")
#pragma GCC diagnostic ignored "-Wsign-compare"
#include <bits/stdc++.h>
using namespace std;
using i64 = int_fast64_t;
#define rep(i, n) for (i64 i = 0; i < (i64)(n); ++i)
#define reps(i, s, n) for (i64 i = s; i < (i64)(n); ++i)

void solve() {
    int r;
    cin >> r;
    cout << 3 * r * r << "\n";
}
int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    // cout << fixed << setprecision(15);
    solve();
}