#include <bits/stdc++.h>

using namespace std;

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

const int NMax = 2e6 + 5;

int k;
bool viz[NMax];

void Ciur(int n){
    k = 1;
    for(int i = 4; i <= n; i = i + 2){
        viz[i] = 1;
    }
    for(int i = 3; i <= n; i = i + 2){
        if(viz[i] == 0){
            k++;
            for(int j = 2 * i; j <= n; j = j + i){
                viz[j] = 1;
            }
        }
    }
}

int main(){
    int n, ans = 0;
    fin >> n;
    Ciur(n);
    fout << k;
    return 0;
}