神奇数

import java.util.Arrays;
import java.util.Scanner;

public class Main {

    public static boolean IsPrime(int a){
        boolean flag = true;
        if ( a <= 1){
            flag = false;
        }else if(a == 2){
            flag = true;
        }else{
            for (int i = 2 ; i < a ; i++){
                if ( a % i == 0){
                    flag = false;
                    break;
                }
            }
        }
        return flag;
    }

    public static boolean check(int a){
        int[] A = new int[5];
        Arrays.fill(A, 0);
        int cnt = 0;
        while(a != 0){
            A[cnt++] = a % 10;
            a /= 10;
        }
        /*for ( int i = 0 ; i < cnt ; i++){
            System.out.print(A[i]+" ");
        }*/
        //System.out.println();
        for (int i = 0 ; i < cnt ; i++){
            for ( int j = 0 ; j < cnt && j != i ; j++){
                int tmp1 = A[i]*10 + A[j];
                int tmp2 = A[j]*10 + A[i];
            //  System.out.println(tmp1+"    "+tmp2);
                if (IsPrime(tmp1) && tmp1 > 10){
                //  System.out.println(tmp1+"是神奇数");
                    return true;
                }
                if (IsPrime(tmp2) && tmp2 > 10){
                //  System.out.println(tmp2+"是神奇数");
                    return true;
                }
            }
        }
        return false;
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in = new Scanner(System.in);
        int start = in.nextInt();
        int end = in.nextInt();
        int cnt = 0;
        for ( int i = start ; i <= end ; i++){
            if (check(i)){
                cnt++;
            }
        }
        System.out.println(cnt);

        in.close();
    }

}