#include <iostream>
#include <fstream>

using namespace std;

ifstream in("ciur.in");
ofstream out("ciur.out");

int sir[2000000]={0};

int main()
{
    int n,i,multiplu,numarul;
    in >> n;

    numarul = n - 1;
    for(i=2; i<=n; i++)
    {
        if(sir[i] == 0)
        {
            multiplu = i;
            while(multiplu+i<=n)
            {
                multiplu += i;
                if(sir[multiplu] == 0)
                {
                    numarul -= 1;
                }
                sir[multiplu] = 1;
            }
        }
    }
    out << numarul;
}