#include<iostream>
#include<stdlib.h>
#include<math.h>
#include<string.h>
#include<vector>
using namespace std;

int v[6];

int ciur[1000010];
vector<int> primes;

bool check(int i)
{
	vector<int> vec,vec1;

	while (i)
	{
		vec.push_back(i % 10);
		i /= 10;
	}
	for (int i = vec.size()-1; i >=0;--i)
		vec1.push_back(vec[i]);

	for (int i = 1; i < (1 << (vec1.size())); ++i)
	{
		int p = 0;
		for (int j = 0; j < vec1.size(); ++j)
		{
			if (((i&(1 << j))))
			{
				p = p * 10 + vec1[j];
			}
		}

		if (ciur[p])
			return false;
	}

	return true;
}

int main()
{

	int l, r;

	cin >> l >> r;

	ciur[1] = 1;
	ciur[0] = 1;

	for (int i = 2; i <= 1000000; i++)
	{
		for (int j = i + i; j <= 1000000; j += i)
			ciur[j] = 1;

		if (!ciur[i])
			primes.push_back(i);
	}
	int nr = 0;
	for (int i = 0; i < primes.size(); ++i)
	{
		if (l <= primes[i] && primes[i] <= r && check(primes[i]))
		{
			++nr;
		}
	}

	cout << nr;

	return 0;
}