/*
TASK: rprimes
LANG: C++
*/ 
#include<stdio.h>
long a,b,i,j,tmp,tmp1;
int main(){
    int flag=0,flag1=0,br=0,k;
    scanf("%ld%ld",&a,&b);
    for(i=a;i<=b;i++){
        k=0;
        
        
        tmp=i;
        flag1=0;
        while(tmp>0){
            tmp1=tmp; 
            if((tmp%2==0&&tmp!=2)||
            (tmp%3==0&&tmp!=3)||
            (tmp%5==0&&tmp!=5)||
            (tmp%7==0&&tmp!=7)||
            (tmp%11==0&&tmp!=11)||
            (tmp%13==0&&tmp!=13)||
            (tmp%17==0&&tmp!=17)||
            (tmp%23==0&&tmp!=23)||
            (tmp%31==0&&tmp!=31)){flag1=1;flag=0;break;}
            while(tmp1>1){
                if((tmp1%10)%2==0&&(tmp1%10)!=2){flag1=1;flag=0;break;}
                else tmp1=tmp1/10;}
            for(j=2;j<tmp;j++){
                if(tmp%j==0){flag=1;break;}}
            if(flag==1||tmp==1){flag1=1;flag=0;break;}
            else tmp=tmp/10;
            }
        if(flag1==0&&tmp!=1)br++;
    }
    printf("%d\n",br);

    return 0;
}
        
        
    
    
