type vector=array[1..2000000]of 0..1;
var n,nr,j,i:longint;a:vector;
    f,g:text;
begin
assign(f,'ciur.in');
reset(f);
read(f,n);nr:=0;
for i:=2 to n do
   begin
     if (a[i]<>1)or(i=2) then
          begin
          a[i]:=0;
          inc(nr);
          j:=i;
          repeat
          inc(j,i);
          a[j]:=1;
          until j>=n;
      end;
   end;
close(f);
assign(g,'ciur.out');
rewrite(g);
writeln(g,nr);
close(g);
end.