#include<iostream>
#include<fstream>
#include<stdlib.h>
using namespace std;
int main()
  {
    FILE*d=fopen("ciur.in","r");
    FILE*o=fopen("ciur.out","w");
    bool s[2000002];
    int n,p;
    fscanf(d,"%d",&n);
    p=n;
    for(long i=1;i<=n;i++) s[i]=true;
    for(long i=2;i<=n;i++)
      for(long j=2;j<=(n/2);j++)
        {
          if((i*j<=n)&&(s[i*j]=true)) p--;
          s[i*j]=false;
        }
    fprintf(o,"%d",p+2);
    fclose(d);fclose(o);
    return 0;
  }