백준 2292번: 벌집

package BOJ.step8;

import java.util.Scanner;

public class BOJ2292 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        long n = sc.nextLong();
        long k = 1;
        long v = 1;

        while (n > k) {
            k += 6*v;
            v++;
        }
        System.out.println(v);
    }
}

껍질당 6n씩 개수가 늘어남