#include <iostream>
#include <fstream>
using namespace std;

int main()
{ifstream fin("input.in");
ofstream fout("output.out");
    int v[1000],a,b,d,i,s=0,c;
   cin>>a>>b;


   for(i=a;i<=b;i++){
        c=0;
    for(d=1;d<=v[i];d++){
     if(v[i]%d==0)
        c++;}
    if(c==2 && v[i]<10)
        s=s+v[i];
        if(c==2 && v[i]>=10)
    {        while(v[i]!=0){
        s=s+v[i]%10;
        v[i]=v[i]/10;}}}
        cout<<s;
    return 0;
}