program ciur;
var a:array[1..2000000] of boolean;
   n,i,k,j:longint;
   f,g:text;
begin
  assign(f,'ciur.in'); reset(f); readln(f,n); close(f);
  assign(g,'ciur.out'); rewrite(g);
  for i:=2 to n do a[i]:=true; k:=0;
  for i:=2 to n do
    if a[i] then begin
             inc(k);
             j:=i;
             repeat
              j:=j+i;
              a[j]:=false;
             until j>n;
             end;
  writeln(g,k);
  close(g);
end.