/*
TASK:rprimes
LANG:C++
*/
#include<iostream.h>
int ifprime(long l)
{long h=2,brz=0;
 while(h<l)
{if(l%h==0) return 0;
h++;
}
return 1;
}
int main()
{long i,a,b,flag,k,br=0;
cin>>a>>b;
for(i=a;i<=b;i++)
{flag=1;
if(ifprime(i))
{k=i;
while(k>9)
{k/=10;if(!ifprime(k)) {flag=0;break;}}
if(i<10) br++;else if(ifprime(k) && flag==1 && k!=1) br++;
}}
cout<<br;
/*long a,b,i;
cin>>a>>b;
for(i=a;i<=b;i++)
if(ifprime(i)) cout<<i<<' ';*/
system("pause");
}