[백준_JAVA] 2292 벌집

import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
    	Scanner sc = new Scanner(System.in);
    	 	
    	int N = sc.nextInt();
    	int start = 1;
    	int range = 2;
    	
    	while(range <= N) {
    		range = range + (6*start);
    		start++;
    	}
    	System.out.println(start);
    	
        sc.close();
    }
}

범위가 6배씩 늘어나는 규칙을 발견한다.