#include <iostream>
#include <fstream>
using namespace std;
int n,x,i,nr;
bool v[10000000];
int main()
{ifstream f("ciur.in");
ofstream g("ciur.out");
    f>>n;
    nr=n;
for(i=2;i*i<=n;i++){
if(v[i]==0) {
for(x=i*i;x<=n;x+=i){
        if(v[x]==0) nr--;
        v[x]=1;}
}
}g<<nr-1;

}