# include <iostream>
# include <cstring>
using namespace std;

bool isp[100000010];

void getprime()
{
    memset(isp, true, sizeof(isp));
    isp[0] = isp[1] = false;
    for (int i = 2; i <= 100000000; i++)
    {
        for (int j = 2; i * j <= 100000000; j++)
        {
            isp[i * j] = false;
        }
    }
    return;
}

int main()
{
    int n, ans = 0;
    cin >> n;
    for (int i = 1; i <= n; i++)
        if (isp[i])
            ans++;
    cout << ans;
    return 0;
}

写的是线筛，只对了一个点