#import<fstream>
std::ifstream f("ciur.in");std::ofstream g("ciur.out");int n,i=3,j,r=1;bool P[2000005];int main(){for(f>>n;i<=n;i++)if(!P[i]&(i&1))for(j=i,++r;j<=n;P[j]=1,j+=i);g<<r;}