#include <iostream>
#include <fstream>

using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
int main()
{
    int n,prim,nr=1;
    in>>n;
    bool v[n+1];
    for(int i=3;i<=n;i=i+2)
    {
        for(int j=2;j*i<=n;j++)
        {
            if(v[i]==1)
            {
                nr+=1;
                v[i*j]=0;
            }
        }
    }
    out<<nr;
    return 0;
}