program Project2;
var
t : array of integer;
n, j, k, i, l : integer;
f, g : text;
procedure sort();
 var
 max, min, pamat, o : integer;
begin
  for i := 1 to n do
  begin
  j := i + 1;
      while j <= n do
      begin
      if t[i] < t[j] then
      begin
      pamat := t[i];
      t[i] := t[j];
      t[j] := pamat;
      end;
      inc(j);
      end;
  end;
end;
procedure kinz();
var
ii, jj, rizn, o : integer;
begin
rizn := 100000;
for ii := 1 to n do
begin

 for jj := 1 to n do
 begin
  o := t[ii] - t[jj];
  if (o < rizn) and ((jj - ii) > (k - 2)) and (o > 0) then
   begin
   rizn := o;
   end;
 end;
end;
writeln(g, rizn);
end;
begin
assign (f, 'holy.in');
reset(f);
read(f, n, k);
setlength(t, n + 1);
assign(g, 'holy.out');
rewrite(g);
for i := 1 to n do
 read(f, t[i]);
i := 1;
j := 1;
sort();
kinz();
close(g);
  { TODO -oUser -cConsole Main : Insert code here }
end.