#include <fstream>
#define m 100000000/8 + 1
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
long long n, i, j;
long nr = 1;
static char p[m];
int main ()
{
    f >> n;
    for (i = 1; ((i * i) << 1) + (i << 1) <= n; i += 1)
    {
        if ((p[i >> 3] & (1 << (i & 7))) == 0)
        {
            for (j = ((i * i) << 1) + (i << 1); (j << 1) + 1 <= n; j += (i << 1) + 1)
            {
                p[j >> 3] |= (1 << (j & 7));
            }
        }
    }
    for (i = 1; 2 * i + 1 <= n; ++i)
       if ((p[i >> 3] & (1 << (i & 7))) == 0)
           nr ++;
    g << nr;
    return 0;
}