#include <bits/stdc++.h>

using namespace std;

ifstream f("ciur.in");
ofstream g("ciuri.out");

const int NMax = 2e6 + 5;






            /*
             *   _ _ _ _ _ _ _
             *  |             |
             *  |             |   __
             *  |         _ _ |  / _|
             *  |        |    |  | |
             *  |_ _ _ _ |    |_ | | _ _ _ _ _ _
             *  |        |    |                 |
             *  |        |_ _ |                 |
             *  |       /     \      _ _        |
             *  |_ _ _ /       \_ _ /   \_ _ _ _|
             *         |       |   |     |
             *          \ _ _ /     \ _ /
             */


int k;
int prime[NMax];
int viz[NMax];

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

int main(){
    int n;
    f >> n;
    tractor(n);
    g << k;
    return 0;
}