program Zadacha;

{$APPTYPE CONSOLE}

uses
  SysUtils;
 var i,j,n,m,r:integer;
 A:array[1..100000] of integer;
 f1,f2:text;
begin
  { TODO -oUser -cConsole Main : Insert code here }
 assign(f1,'holy.in');
 assign(f2,'holy.out');
 reset(f1);
 rewrite(f2);
 read(f1,n,m);
 for i:=1 to n do
 begin
  read(f1,A[i]);
 end;
 for i:=1 to n-1 do
 begin
  for j:=i+1 to n do
  begin
   if A[i]>A[j] then
   begin
    r:=A[i];
    A[i]:=A[j];
    A[j]:=r;
   end;
  end;
 end;
 r:=1000000010;
 for i:=1 to n-m do
 begin
  if (A[i+m-1]-A[i])<r then r:=A[i+m-1]-A[i];
 end;
 writeln(f2,r);
 close(f1);
 close(f2);
end.