#include <fstream>
#include <cmath>
using namespace std;
ifstream(f)("ciur.in");
ofstream(g)("ciur.out");
int i,n,a,j;
bool s[2000005];
int main()
{
    f>>n;
    for (i=1; i<=2000002; i++)
        s[i]=0;
    s[1]=1;
    for (i=4;i<=n;i=i+2)
        s[i]=1;
    for (i=1; i<=n; i+=2)
    {
        if (!s[i])
            for (int j=2*i; j<=n; j+=i) s[j]=1;
    }
    for(i=1; i<=n; i++)
        if (s[i]==0)
        {
            a++;
        }
    g<<a;
    f.close();
    g.close();
    return 0;
}