#include <math.h>
#include <iostream>
using namespace std;
long long ind, all;
long long a, b, i, szam, p = 1, x=1;
bool prim(long long x)
{
    bool ok = true;
    long long i;
    if(x == 0 or x == 1) return false;
    for(i = 2; i * i <= x; i ++)
        if(x % i == 0)
        {
            ok = false;
            break;
        }
    return ok;
}

int main()
{
    cin >> a >> b;
    ind = log2(a) + 1;
    all = log2(b);
    for(i = 1; i <= ind; i ++)
        p = p * 2;
    if(prim(ind))
    {
        szam = szam + p - a;
    }
    for(i = ind; i < all; i ++)
        if(prim(i + 1))
        {
            szam = szam + p;
            p = p * 2;
        }
        else p = p * 2;
    if(prim(all + 1)) szam = szam + b - p+1;
    cout << szam << " ";
    return 0;
}