#include <fstream>

using namespace std;

bool ciur2[1000000];
long long int tmp2,j,index, n, i, nmax, k,l, tmp;

int main()
{
    ifstream f("ciur.in");
    ofstream g("ciur.out");
    f>>n;
    if(n%2==1)
    nmax=n/2;
    else
        nmax=n/2-1;
    for(i = 1; i<=nmax; ++i)
    {
    if(ciur2[i] == 1) continue;
    tmp = 2*i+1;
    for(j = tmp*tmp; j<=n; j+=tmp)
    {
        if(j%2==1)
            index=j/2;
        else
            continue;
        ciur2[index] = 1;
    }
    }
    for(i=1;i<=nmax;i++)
        if(ciur2[i]==0)
            k++;
    g<<k;
}