import java.io.*;
 
 
public class Main {
	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 
		int N = Integer.parseInt(br.readLine());
 
		int sum =0;
 
		for(int i=0; i<2140000000; i++) {
			sum += 1+(6*i);
			if(sum>=N) {
				System.out.println(i+1);
			    System.exit(0);
			}
 
		}
	         br.close();
  }
}