#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
bool *sieve;
int main()
{
    int n, count = 0;
    fin>>n;
    sieve = new bool[n]();
    for(int i = 2; i< n; i++) sieve[i] = 0;
    for(int i = 2; i< n; i++)
    {
            if(sieve[i] != 0) continue;
            for(int j = 2; j< n/i; j++)
            {
                    if(sieve[i*j] == 0){sieve[i*j] = 1; count++;}
            }
    }
    fout<<n-3-count<<endl;
    return 0;
}