#include <iostream>
#include <fstream>
using namespace std;
bool arr[2000000];
int main()
{
    ifstream fin("ciur.in");
    ofstream fout("ciur.out");
    int n;
    fin>>n;
    for(int i = 2; i< n; i++)
    {
        for(int j = 2; j< n; j++)
        {
            if(i*j >= n) break;
            if(arr[i*j] == 0) arr[i*j] = 1;
        }
    }
    int count = 0;
    for(int i =2; i< n; i++)
    {
        if(arr[i] == 0) count++;
    }
    fout<<count<<endl;
}