#include <iostream>
#include <fstream>
#include <conio.h>
#include <stdlib.h>
#include <string.h>
#include <list>
#include <bitset>
#include <vector>
using namespace std;

int a, b, s[] = {2, 3, 5, 7, 23, 37, 53, 73}, ans;

int main(){

scanf("%d %d", &a, &b);

for(int i = 0; i < 8; i++){
    if(a <= s[i] && s[i] <= b) ans++;
}

printf("%d", ans);

return 0;
}