#include <iostream>
#include <fstream>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
int v[2000000];
int main()
{
    int n,nr=0,i,j;
    in>>n;
    for(i=2;i<=n;i++)
    for(j=i+1;j<=n;j++)
    {
        if(j%i==0)
        v[i]=1;
    }
    for(i=2;i<=n;i++)
    {
        if(v[i]==0)
        nr++;
    }
    out<<nr-1;
    return 0;
}