#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<vector>
#include<set>
#include<map>

using namespace std;

#define x first
#define y second

int ans, a, b;

int main (){
    
    scanf("%d%d",&a,&b);
    int v[7] = {2,3,5,7,23,37,53};
    for(int i = 0; i < 7; i++)
        if(a <= v[i] && v[i] <= b)
            ans++;
    printf("%d\n", ans);
    
    return 0;
}