#include <iostream>
#include <fstream>

using namespace std;

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

int main()
{
    int n, nr = 1, v[2000005], x;
    fin >> n;

    for(int i = 0; i <= n; i++) {
        v[i] = 1;
    }

    for(int i = 3; i <= n; i++) {
        if(i % 2 == 0){
            v[i] = 0;
        } else if(v[i] == 1) {
            x = i * 2;
            while(x <= n) {
                v[x] = 0;
                x += i;
            }
        }
    }

    for(int i = 2; i <= n; i++){
        if(v[i] == 1) {
            nr++;
        }
    }

    fout << nr;

    return 0;
}