#include <iostream>
#include <fstream>
#include <bitset>
#define p 1999999973
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
int n;
bitset <2000005 >viz;
int ciur(int n){
        int i,j,nrprime=0;
        nrprime=1;
        for(i=4;i<=n;i+=2) viz[i]=true;
        for(i=3 ;i*i<=n;i+=2){
            if(viz[i]==0) for(j=i*i; j<=n;j=j+2*i) viz[j]=true;

        }
        return n-viz.count()-1;


}


int main()
{
    in>>n;
    out<<ciur(n);
    return 0;
}