import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

/**
 * Created by spenteleiciuc on 4/13/2017.
 */
public class prog {
    public static void main(final String[] args) {
        java.util.Scanner scan = new java.util.Scanner(System.in);
        int a = scan.nextInt();
        int b = scan.nextInt();
        if (a > 317) System.out.println(0);
        else {
            Set<Integer> numbers = new HashSet<Integer>(Arrays.asList(3,5,7,11,13,17,23,31,37,53,71,73,113,131,137,173,311,317));
            int sum = 0;
            for (int i = a; i < 318; i++) {
                if (numbers.contains(i)) sum++;
            }
            System.out.println(sum);
        }
    }
}