//#include <iostream>
#include <fstream>

using namespace std;

fstream in("ciur.in",ios::in);
fstream out("ciur.out",ios::out);

int main()
{
    int n,i,j,k=1;
    char ciur[2000001]={};

    in>>n;

    for(i=2;i*i<=n;i++)
        for(j=i*i;j<=n;j=j+i)
        {
            if(ciur[j]==0)
                k++;
            ciur[j]=1;
        }
    out<<n-k;

    return 0;
}