#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

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

int main(){
    int N, k = 0, factor = 2;
    vector<int> v;
    fin>>N;

    v.resize(N);
    for(int i = 0; i < N; ++i) v[i] = i + 2;
    while(v.size() > 0)
    {
        for(int i = 0; i < v.size(); ++i){
            if(v[i] % factor == 0) v.erase(v.begin() + i);
        }
        factor = v[0];
        k++;
    }
    cout<<k - 1;

    return 0;
}