#include <bits/stdc++.h>

using namespace std;

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

const int NMAX = 2 * 1e6 + 1;

int prim(int x)
{
    for(int d = 2; d * d <= x; d++)
        if(x % d == 0)
            return 0;
    return 1;
}

int main()
{
    int n, nr = 1;
    fin>>n;
    vector <int> a(n + 1);
    for(int i = 3; i <= n; i += 2){
        for(int j = i + i; j <= n; j += i)
            a[j] = 1;
    }
    for(int i = 3; i<=n; i+=2)
        if(!a[i])
            nr++;
    fout<<nr;

    return 0;
}