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

ifstream in("ciur.in");
ofstream out ("ciur.out");
const int N=10000001;

bitset <N> primes;
int n,i,j,nr;
using namespace std;

int main()
{
    nr=0;
    cout << "n=";
    cin>>n;
    primes [1]=1;
    for (i=4;i<=n;i+=2)
          primes [i]=1;
    for (i=3;i*i<=n;i+=2)
        if (!primes [i])
                for (j=i<<1;j<=n;j+=i)
                    primes [j]=1;
    for (i=1;i<=n;i++)
        if (!primes[i]) nr++;
        cout<<nr;
    return 0;
}