var
  n,i,p:longint;
  ans:int64;
  d:array[0..100000]of int64;

begin
  assign(input,'mushroom.in'); reset(input);
  assign(output,'mushroom.out'); rewrite(output);
  readln(n);
  d[2]:=1;
  for i:=2 to n do
  begin
    if i mod 2=0 then p:=1
    else p:=2;
    repeat
      d[p]:=d[p-1]+d[p+1];
      inc(p,2);
    until p>i+1;
  end;

  ans:=0;
  for i:=1 to 20000 do
  if i mod 2<>n mod 2 then
  inc(ans,d[i]);
  writeln(ans);
  close(input);
  close(output);
end.