#include <bits/stdc++.h>
#define mp make_pair 
using namespace std;

ifstream fin("ciur.in");
ofstream fout("ciur.out");

int n;
int ans = 0;
bool ciur[2000001];
void pre(int n)
{
    ciur[0] = ciur[1] = 1;
    for(int i = 4; i <= n; i+= 2)
        ciur[i] = 1;
    for(int i = 3; i * i <= n; i += 2)
        if(ciur[i] == 0)
            for(int j = i * i; j <= n; j+= i + i)
                ciur[j] = 1;
}

int main()
{
    fin >> n;
    pre(n);
    for(int i = 1; i <= n; i++)
        ans += ciur[i];
    ans = n - ans;
    fout << ans << "\n";
    fin.close();
    fout.close();
    return 0;
}