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 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>

//B問題

int cal(int N, int D)
{
	int i=0;
	int total = 0;
	total = N;
	while (1)
	{
		if (total <= (2 * D + 1)) {
			return i+1;
		}
		
		total = total -(2 * D + 1);
		if (total <= (2 * D + 1)) {
			i++;
			return i + 1;
		}
		if (total <= 0) {
			i++;
			return i;
		}
		
		i++;
	}
}

int main()
{
	int N, D;

	scanf("%d %d", &N, &D);

	printf("%d\n", cal(N, D));
	return 0;
}