program pascal;
var f,g:text;
    i,d,n,nr,rez,j:longint;
    v:array[1..2000000] of longint;
begin
 assign(f,'ciur.in'); reset(f);
 assign(g,'ciur.out'); rewrite(g);
 read(f,n);
 rez:=0;
 for d:=2 to trunc(sqrt(n)) do
  if v[d]=0 then
              begin
               for j:=2 to n div d do v[d*j]:=1;
              end;
 for i:=2 to n do
       if v[i]=0 then inc(rez);

 write(g,rez);
 close(f);
 close(g);
end.