#include <iostream>
#include <fstream>
using namespace std;
char a[2000001];
int n,k,p,s,i;
int main()
{
    ifstream fin("ciur.in");
    ofstream fout("ciur.out");
    fin>>n;k=2;
    while(k<=n)
    {
    //    cout<<k<<endl;
        a[k]=1;
        p=k;
        s++;
        while(p+k<=n)
        {
            p=p+k;
            a[p]=1;
        }
        for(i=k;i<=2000000;i++)if(a[i]==0){k=i;i=2000001;}
        if(i==2000001)k=2000001;
    }
    fout<<s;
  //  cout<<sizeof(a);
    fin.close();
    fout.close();
    return 0;
}