#include <bits/stdc++.h>
#define MAXN 2000005

using namespace std;

ifstream in ("ciur.in");
ofstream out ("ciur.out");

int n;
bitset <MAXN> v;

int ciur()
{
    int c=0;
    for (int i=3; i<=n; i+=2)
        if (!v[i])
        {
            c++;
            for (int j=3*i; j<=n; j+=i<<1)
                v[j]=1;
        }
    return c+1;
}

int main()
{
    in >> n;
    out << ciur();
    return 0;
}