program ssss;
var f,g:text;
    n,numar,nr,c:longint;
    bifat:array[1..2000000] of boolean;
begin
assign(f,'ciur.in'); reset(f);
assign(g,'ciur.out'); rewrite(g);
readln(f,n);
c:=0;
numar:=2;
  while numar<=n do
    begin
       nr:=numar;
      while nr<=n do
        begin
        bifat[nr]:=true;
        nr:=numar+nr;
        end;
      while bifat[numar]=true do
       numar:=numar+1;
      c:=c+1;
    end;
    write(g,c);
close(f);
close(g);
end.