#include<fstream>

using namespace std;

ifstream cin("ciur.in");
ofstream cout("ciur.out");

bool v[2000000];
int i,j;

int sieve(int n)
{
      v[1]=v[0]=1;
      int count=1;
  for(i=4;i<=n;i+=2)
  {
      v[i]=1;
      count++;
  }
  for(i=3;i<=n;i+=2)
        if(v[i]==0)
      for(j=i+i;j<=n;j+=i)
        {
          if(v[j]==0)
              count++;
          v[j]=1;
        }
        return count;
}

int main()
{
  int n;
  cin>>n;
  cout<<n-sieve(n);
}