#include<iostream>
#include<cmath>
#include<algorithm>
using namespace std;
int sushu(int x)
{
    int i=2;
    while(i<sqrt(x)&&x%i!=0)
{
       i++;
   }
  if(i>sqrt(x)&&x!=1)
   {
        return 1;
    }
    else
   {
        return 0;
    }
 }
 int huiwen(int x)
{
    int sum=0;
    while(x)
{
sum=sum*10+x%10;
 x/=10;
}
return sum;
}
int main()
{
   int r,t=0;
  cin>>r;
   for(int i=11;i<=r;++i)
   {
     if(sushu(i)&&huiwen(i)==i)
            t++;
}
cout<<t;
return 0;
}