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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)




import java.util.*;
import java.io.*;

public class Main {

    private static FastScanner sc = new FastScanner();

    private static int[][] neg8 = new int[][]{{-1, -1}, {0, -1}, {1, -1}, {-1, 0}, {1, 0}, {-1, 1}, {0, 1}, {1, 1}};
    private static int[][] neg4 = new int[][]{{1, 0}, {0, -1}, {-1, 0}, {0, 1}};
    /*  neg4    neg8
     *    3      678
     *   2*0     4*5
     *    1      123
     */
    public static void main(String[] args) {

        long r = sc.nextLong();

        System.out.println((long)(3*Math.pow(r,2)));



    }
}

class FastScanner extends PrintWriter {
    private final InputStream in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;
    FastScanner() {
        this(System.in);
    }

    FastScanner(InputStream source) {
        super(System.out);
        this.in = source;
    }

    boolean hasNextByte() {
        if (ptr < buflen) {
            return true;
        } else {
            ptr = 0;
            try {
                buflen = in.read(buffer);
            } catch (IOException e) {
                e.printStackTrace();
            }
            if (buflen <= 0) {
                return false;
            }
        }
        return true;
    }

    int readByte() {
        if (hasNextByte()) return buffer[ptr++];
        else return -1;
    }

    boolean isPrintableChar(int c) {
        return 33 <= c && c <= 126;
    }

    boolean isNewLine(int c) {
        return c == '\n' || c == '\r';
    }

    void skipUnprintable() {
        while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;
    }

    void skipNewLine() {
        while (hasNextByte() && isNewLine(buffer[ptr])) ptr++;
    }

    boolean hasNext() {
        skipUnprintable();
        return hasNextByte();
    }

    boolean hasNextLine() {
        skipNewLine();
        return hasNextByte();
    }

    String next() {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while (isPrintableChar(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }

    char[] nextCharArray(int len) {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }
        char[] s = new char[len];
        int i = 0;
        int b = readByte();
        while (isPrintableChar(b)) {
            if (i == len) {
                throw new InputMismatchException();
            }
            s[i++] = (char) b;
            b = readByte();
        }
        return s;
    }

    String nextLine() {
        if (!hasNextLine()) {
            throw new NoSuchElementException();
        }
        StringBuilder sb = new StringBuilder();
        int b = readByte();
        while (!isNewLine(b)) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }

    long nextLong() {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }
        long n = 0;
        boolean minus = false;
        int b = readByte();
        if (b == '-') {
            minus = true;
            b = readByte();
        }
        if (b < '0' || '9' < b) {
            throw new NumberFormatException();
        }
        while (true) {
            if ('0' <= b && b <= '9') {
                n *= 10;
                n += b - '0';
            } else if (b == -1 || !isPrintableChar(b)) {
                return minus ? -n : n;
            } else {
                throw new NumberFormatException();
            }
            b = readByte();
        }
    }

    int nextInt() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) {
            throw new NumberFormatException();
        }
        return (int) nl;
    }

    char nextChar() {
        if (!hasNext()) {
            throw new NoSuchElementException();
        }
        return (char) readByte();
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    int[] arrayInt(int n) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++) a[i] = nextInt();
        return a;
    }

    long[] arrayLong(int n) {
        long[] a = new long[n];
        for (int i = 0; i < n; i++) a[i] = nextLong();
        return a;
    }

    double[] arrayDouble(int n) {
        double[] a = new double[n];
        for (int i = 0; i < n; i++) a[i] = nextDouble();
        return a;
    }

    void arrayInt(int[]... a) {
        for (int i = 0; i < a[0].length; i++) for (int j = 0; j < a.length; j++) a[j][i] = nextInt();
    }

    int[][] matrixInt(int n, int m) {
        int[][] a = new int[n][];
        for (int i = 0; i < n; i++) a[i] = arrayInt(m);
        return a;
    }

    char[][] mapChar(int n, int m) {
        char[][] a = new char[n][];
        for (int i = 0; i < n; i++) a[i] = nextCharArray(m);
        return a;
    }

    public void close() {
        super.close();
        try {
            in.close();
        } catch (IOException ignored) {
        }
    }
}