program Zadacha;

{$APPTYPE CONSOLE}

uses
  SysUtils;
 var i,j,n,m,r,m1,m2: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);
 if n=m then
 begin
  m1:=1000000010;
  m2:=0;
  for i:=1 to n do
  begin
   read(f1,A[i]);
   if m1>A[i] then m1:=A[i];
   if m2<A[i] then m2:=A[i];
  end;
  writeln(f2,m2-m1);
 end else
 begin
  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+1 do
  begin
   if (A[i+m-1]-A[i])<r then r:=A[i+m-1]-A[i];
  end;
  writeln(f2,r);
 end;
 close(f1);
 close(f2);
end.