#include <bits/stdc++.h>
#define oo 2000000001
using namespace std;

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

int n, cnt, d[5000003];

void Eratostene(int n)
{
    int i, j;
    for (i = 2; i <= n; i++)
    {
        d[i] += 2;
        if (d[i] == 2)
            for (j = 2 * i; j <= n; j += i)
                d[j]++;
    }
}

int main()
{
    ios_base::sync_with_stdio(0);
    fin.tie(0);
    fout.tie(0);
    fin >> n;
    Eratostene(n);
    for (int i = 2; i <= n; i++)
        if (d[i] == 2) cnt++;
    fout << cnt << "\n";
    return 0;
}
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