#include <cstdio>

using namespace std;

long long memo[1000000];


long long snaga(long long a)
{
     if(a<1000000)
     {
                   if(memo[a]!=-1) return memo[a];
                   else
                   {
                       for(long long i=2;i<a;i++)
                       {
                                if(a%i!=0){memo[a]=1; memo[a]+=snaga(i);break;}
                       }
                       return memo[a];
                   }
     }
     else
     {
         for(long long i=0;i<a;i++)
         {
                                if(a%i!=0){return snaga(i)+1;}                                     
         }
     }
}
         





int main()
{
    for(int i=0;i<1000000;i++) memo[i]=-1;
    memo[0]=0; memo[1]=memo[2]=1;
    memo[3]=2;
    long long a,b,rj=0;
    scanf("%lld %lld",&a,&b);
    for(long long i=a;i<=b;i++) rj+=snaga(i);
    printf("%lld\n",rj);
    return 0;
}