#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
const int N=1e6+5;
int cnt;
int prime[]={省略表};
int n,vis[N];
long long l,r;
int main(){
	scanf("%lld%lld",&l,&r);
	for(long long i=0;prime[i]*prime[i]<r+1;i++){
		long long p=prime[i];
		for(long long j=max(2*p,((long long)ceil(double(l)/double(p)))*p);j<r+1;j+=p){
			vis[j-l]=1;
		}
	}
	int ans=0;
	if(l==1) ans--;
	for(long long i=l;i<=r;i++){
		if(!vis[i-l]) ans++;
	}
	printf("%d",ans);
	return 0;
}