#include <bits/stdc++.h>

using namespace std;

const int nmax = 2e6 + 10;
const int Sqrt = 1500;

int n , i , j , ans;
unsigned char low[nmax];
int p[Sqrt+10];

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 <= Sqrt) p[++p[0]] = i;
        }

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

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

    return 0;
}