---

var n,i, ans, m, k, a : integer;
begin 
  read(n);
  read(a);
  m := a;
  k := a;
  for i := 2 to n do
  begin
    read(a);
    if a < m then
      m := a;
    if a > k then
      k := a;
  end;
  ans := (k - m + 1) - n;
  writeln(ans);
end.