#include<cstdio>
#include<fstream>
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<bitset>
#include<deque>
#include<queue>
#include<set>
#include<map>
#include<cmath>
#include<cstring>
#include<ctime>
#include<cstdlib>
#include<unordered_map>

#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define pll pair<ll,ll>
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second

using namespace std;

const int nmax = 2000005;

int n, i, j, sol;
bitset<nmax> viz;

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

    scanf("%d", &n);

    sol = 1;
    for(i = 3; i * i <= n; i += 2)
        if(!viz[i])
        {
            sol++;
            for(j = i; j <= n; j += i)
                viz[j] = 1;
        }

    for(; i <= n; i += 2)
        if(!viz[i])
            sol++;

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

    return 0;
}