/* file: superprimes.c */
/* author: Anastase Luca-George (email: l.anastase@student.rug.nl) */
/* date: 9/23/2024 */
/* version: 2.0 */
/* Description: This program tells how many numbers between a and b are superprimes     */

#include <stdio.h>

/// A function to check whether or not a number is prime
int is_prime(int x)
{
    if(x == 1 || x == 0)
        return 0;
    if(x == 2 || x == 3)
        return 1;
    if(x % 2 == 0 || x % 3 == 0)
        return 0;
    for(int i = 5; i * i <= x; i+=6) // skipping multiples and 2 and 3
        if(x % i == 0 || x % (i + 2) == 0)
            return 0;
    return 1;
}

int main(){

    int a, b, cnt = 0;
    scanf("%d %d", &a, &b);

    /// Iterating through all numbers between a and b
    for(int i = a; i < b; ++ i){

        int f1 = 1;
        int x = i;

        // Checking if a number is superprime
        if(is_prime(x)){
            while(x > 9){
                int sum = 0, c = x;

                while(c){
                    sum+= (c % 10);
                    c /= 10;
                }

                if(!is_prime(sum)){
                    f1 = 0;
                    break;
                }

                x = sum;
            }

            if(f1 == 1){
                cnt++;
                printf("%d\n", cnt);
            }
        }
    }

    printf("%d\n", cnt);

    return 0;
}