#include <iostream>
#include <fstream>
#include <cmath>
using namespace std;
int n,nr,b,a,v[2000001];
ifstream f("ciur.in");
ofstream g("ciur.out");

int main(){
    f>>n;
    a=sqrt(n);
    for(int i=2;i<=a;i++){
        if(v[i]==0){
            b=i*i;
            while(b<=n){
                if(v[b]==0)nr++;
                v[b]=1;
                b=b+i;
            }
        }
    }
    g<<n-nr-1;
    f.close();
    g.close();
return 0;
}