program ciur;
type vector=array[1..2000005] of 0..1;
var prim:vector;
    n,cnt,i,j:longint;
    f,g:text;
begin
assign(f,'ciur.in');reset(f);
assign(g,'ciur.out');rewrite(g);
read(f,n);
cnt:=0;
j:=2;
for i:=2 to n do prim[i]:=1;
for i:=2 to n do if prim[i]=1 then begin
                                   inc(cnt);
                                   while j<=n do begin
                                                 inc(j,i);
                                                 prim[j]:=0;
                                                 end;
                                   end;
writeln(g,cnt);
{for i:=1 to n do write(g,prim[i],' ');}
close(f);close(g);
end.