#include <cstdio>
#include <algorithm>

using namespace std;

int a[16], k;

bool rev ()
{
    for (int i = 1; i < (1 << k); ++i)
    {
        int p = 0;
        for (int j = 0; j < k; ++j)
            if ((1 << j) & i) p = p * 10 + a[j + 1];

        if (p == 1 || p == 0) return false;

        for (int j = 2; j * j <= p; ++j)
            if (!(p % j)) return false;
    }

    return true;
}

int main ()
{
    int aa, bb;
    scanf ("%d %d", &aa, &bb);

    int nr = 0;
    for (int i = aa; i <= min (bb, 9999); ++i)
    {
        k = 0;
        int ci = i;
        for (; ci > 0; ci /= 10)
            a[++k] = ci % 10;

        reverse (a + 1, a + k + 1);

        if (rev ()) ++nr;
    }

    printf ("%d\n", nr);

    return 0;
}