#include <bits/stdc++.h>
using namespace std;
int a, b, ma[100001], dem;
bool kt(int n)
{
    int tong = 0;
    while(n > 0)
    {
        int cs = n % 10;
        if(ma[cs] == 0) return false;
        tong += cs;
        n /= 10;
    }
    if(ma[tong] == 0) return false;
    return true;
}
void sang()
{
    for(int i = 0; i <= b; i++)
        ma[i] = 1;
    ma[0] = 0;
    ma[1] = 0;
    for(int i = 2; i <= b; i++)
        if(ma[i])
            for(int j = i*i; j <= b; j += i)
                ma[j] = 0;
}
int main() 
{
    cin >> a >> b;
    sang();
    for(a; a <= b; a++)
        if(ma[a] && kt(a)) dem++;
    cout << dem;
    return 0;
}

$#khanhtaon$