/*
TASK:rprimes
LANG:C++
*/
#include<iostream.h>
int prime (int x)
{for(int z=2;z<x;z++)
if(x%z==0) return 0;
if(x<2) return 0;
return 1;}
int main()
{long a,b;
long i,j,k;
int br=0;
cin>>a>>b;
for(i=a;i<=b;i++)
{k=i;
while(prime(k) && k>=10)
{k=k/10;}
if(prime(k)) br++;}
cout<<br;
return 0;}