package bohan;
import java.util.Scanner;
public class task4 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in= new Scanner(System.in);
		int a=in.nextInt();
	    int b=in.nextInt(),sum=0;
		while(a%3!=0) {
			a++;

		}

		while(a<b) {
			sum=sum+a;
			a=a+3;
		}
      System.out.println(sum);
	}

}