#include<fstream>
#define nmax 2000000
#include<cstring>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int v[nmax],i,j,nrprime,n;
int main()
{
    fin>>n;
    nrprime=0;
    memset(v,0,sizeof v);
    for(i=3;i<=n;i++)
    {
        if(v[i]!=0 && i%2!=0)
        {
            for(j=2;j<=n/2;j++)
                v[i*j]=1;
        }
    }
    for(i=3;i<=n;i++)
    {
        if(v[i]==0 && i%2!=0)
            nrprime++;
    }
    fout<<nrprime;
    fin.close();
    fout.close();
    return 0;
}