#include <fstream>
using namespace std;
ifstream cin("ciur.in");
ofstream cout("ciur.out");

#define nmax 2000010

int n,rez;
bool v[nmax];

int main()
{
    int i,j;
    cin>>n;
    for (i=2;i<=n;i+=2)
        v[i]=1;
    for (i=3;i<=n;i+=2)
        if (!v[i])
        {
            rez++;
            for (j=i*i;j<=n;j+=2*i)
                v[j]=1;
        }
    cout<<rez+1;
}