#include <iostream>
#include <fstream>
#include <bitset>
using namespace std;
bitset <2000000> b;

int main()
{
    b[1]=1;
    long n,i,j,x;
    ifstream f("ciur.in");
    ofstream g("ciur.out");
    f>>n;
    i=2;
    while(i<=n)
      {
          for(j=i+1;j<=n;j++)
            if(j%i==0)
               b[j]=1;
            x=i;
           for(j=i+1;j<=n;j++)
             if(b[j]==0)
                {
                    i=j;
                    j=n+1;
                }
            if(x==i)
              i=n+1;
      }
      g<<n-b.count();
      f.close();
      g.close();
    return 0;
}