#include <iostream>
using namespace std;

int a,b,cnt;
int main()
{
    cin>>a>>b;
    if (a<=2&&2<=b)
        cnt++;
    if (a<=3&&3<=b)
        cnt++;
    if (a<=5&&5<=b)
        cnt++;
    if (a<=7&&7<=b)
        cnt++;

    if (a<=23&&23<=b)
        cnt++;
    if (a<=37&&37<=b)
        cnt++;
    if (a<=53&&53<=b)
        cnt++;
    if (a<=73&&73<=b)
        cnt++;

    cout<<cnt;
    return 0;
}