#include<iostream>
#include<fstream>
using namespace std;
bool v[1000007];
int main ()
{
    ifstream f("ciur.in");
    ofstream g("ciur.out");
    int i,n,j,s=1;
    f>>n;
    for(i=1;i*2+1<=n/2;i++)
    {
        if(v[i]==0)
        {
        for(j=(i*2+1)*(i*2+1);j<=n;j+=i*2+1)
            if(j%2!=0)
                v[(j-1)/2]=1;
        }
    }
    for(i=1;i*2+1<=n;i++)
        {
            if(v[i]==0)
                s++;
        }
    g<<s;
}