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 Rust (1.15.1) (judge verdict: Accepted)

use std::io;
use std::collections::HashMap;

fn read_line() -> String {
    let mut line = String::new();

    io::stdin().read_line(&mut line)
        .expect("Failed to read line");
    return line;
}
fn to_i(s: &str) -> i64 {
    return s.trim().parse()
        .expect("Please type a number!");
}
fn read_nums() -> Vec<i64>
{
    let line = read_line();
    let items: Vec<&str> = line.split(' ').collect();

    let mut nums: Vec<i64> = Vec::new();

    for item in items {
        nums.push(to_i(item));
    }
    return nums;
}


fn main() {
    //println!("start");
    let nab = read_nums();
    let n = nab[0];
    
    //println!("{}",n);
    let ret = 3*n*n;
    
    print!("{}", ret);
    
    
}