#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;

const int nMax = 2e6 + 7;
const int sq = sqrt(nMax);

bool ciur[nMax];
int n, ans;

main()
{
    ifstream cin("ciur.in");
    ofstream cout("ciur.out");
    ciur[0] = true;
    ciur[1] = true;
    for (int i = 2; i <= sq; ++i)
        if (!ciur[i])
            for (int j = i; j * i <= nMax; ++j)
                ciur[j * i] = true;
    cin >> n;
    for (int i = 1; i <= n; ++i)
        ans += (ciur[i] == false ? 1 : 0);
    cout << ans;
}