#include <bits/stdc++.h>
using namespace std;
bool IsPrime(int x){
if(x == 1)
return false;
if(x == 2 || x == 3)
return true;
if(x % 6 != 1 && x % 6 != 5)
return false;
int x_sqrt = (int)sqrt(x);
for(auto i = 5;i<x_sqrt + 1;i += 6){
if(x % i == 0 || x % (i+2) == 0)
return false;
}
return true;
}
bool IsPalindrome(int x){
string x_str = to_string(x);
int sz = x_str.size();
if(sz == 1)
return true;
int mid = x_str.size() / 2;
int left = mid - 1,right = mid + 1;
if(x_str.size() % 2 == 0)
right = mid;
while(left >= 0 && right < sz){
if(x_str[left] != x_str[right])
return false;
--left;
++right;
}
return true;
}
int main(){
int L,R;
while(cin >> L >> R){
int cnt = 0 ,i = L;
for(;i <= R;++i){
if(IsPrime(i) && IsPalindrome(i))
++cnt;
}
cout<<cnt<<endl;
}
return 0;
}
