#include <iostream>
bool prime(int n){
int i;
if(n<2) return false;
if(n==2 || n==3) return true;
if(!(n%2)) return false;
for(i=3;i<n;i+=2)
if(!(n%i)) return false;
return true;
}
void main(void){
int a,b,i,n,sum;
char str[12]="",*ptmp;
cout << "Type a & b(a<b)...\n";
cin >> a >> b;
for(sum=0,i=a,b++;i<b;i++){
for(n=0,itoa(i,str,10),ptmp=str;*ptmp;n+=*ptmp++ -'0');
if(prime(n)) sum++;
}
cout << sum << endl;
}