#include <iostream>
#include <fstream>
using namespace std;
int main () {
ifstream in("ciur.in");
ofstream out("ciur.out");
long long a,b,N,i,contor=0;
in>>N;
bool estePrim = true;

for (a=2;a<N;a++)
{ int i=0;

for (b=1;b=a/2;b++)
    {   bool estePrim = true;
        if ( a % b == 0 ) { estePrim = false;
 break;
 }
        if( estePrim == true)
            contor++;

    }
if (i==1) contor++;
}
out<<contor;
return 0;
}