#include <iostream>
#include <vector>
#include <bitset>
#include <fstream>
#define LL long long
#define Nmax 2000005


using namespace std;
vector <int> pr;
bitset <Nmax> isprime;
ifstream fin ("ciur.in");
ofstream fout ("ciur.out");

int N;
void ciur()
{
    for(int LL i=2;i<=Nmax;i++)
    {
        if(isprime[i]==0)
        {
        for(int LL j=i;j<=Nmax;j+=i)
            isprime[j]=1;
        }
       pr.push_back (i);
    }
}

int main()
{
    int N,i,c=0;
  cin>>N;
  ciur();
  for(i=2;pr[i]<=N;i++)
    cout<<c++;
    return 0;
}