var n, i, t: Longint;
          a: array[1..1000] of Longint;
     sortOk: boolean;
          s: Longint;

begin
 readln(n);
 for i := 1 to n do
  read(a[i]);

 repeat
  sortOk := true;
  for i := 2 to n do
   if a[i] < a[i - 1]
    then begin
          sortOk := false;
          t := a[i - 1];
          a[i - 1] := a[i];
          a[i] := t;
         end
 until sortOk;

 s := 0;
 for i := 1 to n div 2 do
  s := s + a[n + 1 - i] - a[i];

 writeln(s)
end.
