var f:text;
    n,j,i,nr:integer;
    v:array[1..30000]of byte;
begin
assign(f,'ciur.in');
reset(f);
read(f,n);
close(f);
fillchar(v,sizeof(v),1);
for i:=2 to trunc(sqrt(n)) do
 if v[i]=1 then
  begin
   j:=2;
   while j*i<=n do
    begin
     v[i*j]:=0;
     inc(j);
    end;
   end;
 for i:=2 to n do
 if v[i]=1 then
  nr:=nr+1;
assign(f,'ciur.out');
rewrite(f);
write(f,nr);
close(f);
end.