#include<fstream>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
int n, k;
bool v[2000001];
int main()
{
    int i, j;
    f>>n;
    v[2]=1;
    for(i=3;i<=n;i+=2)
    {
        if(v[i]==0)
        {
            for(j=i+i;j<=n;j+=i)v[j]=1;
        }
    }
    for(i=1;i<=n;i+=2)if(v[i]==0)k++;
    g<<k;
    f.close();
    g.close();
    return 0;
}