//Code by Patcas Csaba

#include <vector>
#include <string> 
#include <set> 
#include <map> 
#include <queue> 
#include <bitset> 
#include <stack>
#include <list>

#include <numeric> 
#include <algorithm> 

#include <cstdio>
#include <fstream>
#include <iostream> 
#include <sstream> 
#include <iomanip>

#include <cctype>
#include <cmath> 
#include <ctime>
#include <cassert>

using namespace std;

#define LL long long
#define PII pair <int, int>
#define VB vector <bool>
#define VI vector <int>
#define VD vector <double>
#define VS vector <string>
#define VPII vector <pair <int, int> >
#define VVI vector < VI >
#define VVB vector < VB >

#define FORN(i, n) for(int i = 0; i < (n); ++i)
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define REPEAT do{ 
#define UNTIL(x) }while(!(x)); 

#define SZ size()
#define BG begin() 
#define EN end() 
#define CL clear()
#define X first
#define Y second
#define RS resize
#define PB push_back
#define MP make_pair
#define ALL(x) x.begin(), x.end()

#define IN_FILE "a.in"
#define OUT_FILE "a.out"

int a, b, sol = 0;

bool isPrime(int x)
{
  int gyok = sqrt(x);
  for (int i = 2; i <= gyok; ++i)
  {
    if ((x % i) == 0)
    {
      return false;
    }
  }
  return true;
}

void back(int n, int pow10, int nr3, int nr7)
{
  if (nr3 > 1) return;
  if (nr7 > 1) return;
  if (n > b || pow10 == 1000000000) return;
  if (pow10 == 1)
  {
    back(2, 10, 0, 0);
    back(3, 10, 1, 0);
    back(7, 10, 0, 1);
  }
  else
  {
    if (a <= n && n <= b && isPrime(n))
    {
      ++sol;
      //cerr << n << endl;
    }
    back(n * 10 + 3, pow10 * 10, nr3 + 1, nr7);
    back(n * 10 + 7, pow10 * 10, nr3, nr7 + 1);
  }
}

int main()
{
	//Read data
	//freopen(IN_FILE, "r", stdin);
	//freopen(OUT_FILE, "w", stdout);
	
  cin >> a >> b;
  back(0, 1, 0, 0);
  cout << sol;
	//Solve

	//Write data
  

	return 0;
}