#include <bits/stdc++.h>
#define pb push_back
#define NMAX 2005
#define ll long long

using namespace std;

int cf[]={2,3,5,7},nr,a,b;
int numere[10];
map<int,bool> mp;

inline bool isprime(int x) {
	map<int,bool>::iterator it=mp.find(x);
	if(it!=mp.end()) return it->second;

	if(x!=2 && x%2==0) return 0;
	if(x==1) return 0;

	int d=3;
	while(d*d<=x) {
		if(x%d==0) return mp[x]=0;
		d+=2;
	}

	return mp[x]=1;
}

inline bool comb(int pos, int lim, int nr) {
	if(nr && !isprime(nr)) return 0;
	for(int i=pos;i<=lim;++i) {
		if(comb(i+1,lim,nr*10+numere[i])==0)
			return 0;
	}

	return 1;
}

void bkt(int pos, int x) {
	if(pos==9) return;

	for(int i=0+(pos!=0);i<4;++i) {
		numere[pos]=cf[i];

		if(x*10+cf[i]>b) return;
		if(x*10+cf[i]>=a && comb(0,pos,0)) {
			++nr;
			//cout<<x*10+cf[i]<<' ';
		}
		bkt(pos+1,x*10+cf[i]);
	}
}

int main() {
	cin>>a>>b;

	bkt(0,0);
	cout<<nr;

    return 0;
}