//#include <iostream>
#include <fstream>
#include <vector>


using namespace std;
ifstream cin ("ciur.in");
ofstream cout ("ciur.out");

long long n,m,i,j;
vector<bool> x;
void primszita(int n)
{
    int i,j;
    for (i=2;i<=n;++i)
    {
        if (!x[i])
        {
            j=i+i;
            while (j<=n)
            {
                x[j]=true;
                j+=i;
            }
        }
    }
}
int main()
{
    ios::sync_with_stdio(false);
    cin>>n;
    x.resize(n+1);
    x[1]=true;
    primszita(10);
    int db=0;
    for (i=1;i<=n;++i) if (!x[i]) db++;
    cout<<db<<"\n";
    return 0;
}