#include <iostream>
#include <cmath>
using namespace std;

int A, B;
int sol;

bool isprime(int x)
{
    if (x == 2 || x == 3 || x == 5 || x == 7)
        return 1;
    if (x % 2 == 0)
        return 0;
    for (int d = 3; d*d <= x; d+=2)
        if (x % d == 0)
            return 0;
    return 1;
}

void BK(int k, int no)
{
    if (no > B)
        return;
    if (A <= no && no <= B && isprime(no))
        sol++;
    BK(k+1, no*10+2);
    BK(k+1, no*10+3);
    BK(k+1, no*10+5);
    BK(k+1, no*10+7);
}

int main()
{
    cin >> A >> B;
    BK(0, 0);
    cout << sol;
}