#include <bits/stdc++.h>

using namespace std;

const int nmax = 2e6 + 10;

int n , i , ans;
unsigned char low[nmax];
int p[1510];

int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);

    scanf("%d", &n);

    for (i = 2; i <= n; ++i)
    {
        if (low[i] == 0)
        {
            ans++;
            if (i <= 1500) p[++p[0]] = i;
        }

        for (int j = 1; j <= p[0]; ++j)
        {
            int it = p[j];
            if ((it > p[low[i]] && low[i] != 0) || it * i > n) break;
            low[it*i] = j;
        }
    }

    printf("%d\n", ans);

    return 0;
}