#include <fstream>
using namespace std;ifstream f("ciur.in");ofstream g("ciur.out");int main(){int n,s=0,gasit;char nr[2000001];f>>n;for(int i=3;i<=n;i+=2)for(int j=i*i;j<=n;j+=2*i){if(nr[j]!=1)s++;nr[j]=1;}g<<n-(n/2)-s;f.close();g.close();}