#include <fstream>
#include <math.h>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
long long v[2000000],b[100001],i,x,i1,j,ok,i2,med,c,nr,s,n;
short caz;
int main()
{
    f>>n;
    for(i=2;i<=n;i++)
        v[i-1]=i;
    for(i=1;i<=sqrt(n)+1;i++)
    {
        ok=0;
        if(v[i]!=0)
        {
        for(j=2;j<sqrt(v[i]);j++)
        {
            if(v[i]%j==0)
            {
                ok=1;
                break;
            }
        }
        if(ok==0)
            c=2*v[i]-1;
        else
            c=v[i]-1;
        for(j=c;j<n;j=j+v[i])
            v[j]=0;
        }
    }
    nr=0;
    for(i=1;i<=n;i++)
        if(v[i]!=0)
            nr++;
    g<<nr;
    return 0;
}