#include <iostream>
#include  <fstream>
#include    <bitset>
using namespace std;
bitset<2000005>a;
long long i,j,n;

int main()
{   ifstream fin("ciur.in");
    ofstream fout ("ciur.out");
    fin>>n;
    for(i=4;i<=n;i++)
        a[i]=1;
    for(i=3;i*i<n;i=i+2)
    {if(a[i]==0) for(j=i*i;j<=n;j=j+2) a[j]=1;
    }
    j=1;
    for(i=1;i<=n;i=i+2)
    {if(a[i]==0) j++;
    }fout<<j;

    fin.close();
    fout.close();

    return 0;
}