program B;

{$APPTYPE CONSOLE}

uses
  SysUtils;
type
 kol=array[1..1000] of integer;

const
 fin='holy.in';
 fout='holy.out';

var
 fi,fo:text;
 kul:kol;
 kyl:kol;
 n,m,k,i,j,l,r,y,z,d,p:integer;

procedure sort(var arg:kol);
var
q,w,t:integer;
begin
 for q:=1 to 999 do
   for w:=1 to 1000-w do
    if arg[w]>arg[w+1] then begin
     t:=arg[w]; arg[w]:=arg[w+1]; arg[w+1]:=t;
    end;
end;

begin
  assign(fi,fin);
  reset(fi);
  read(fi,n,k);
  for m:=1 to n do begin
   read(fi,l);
   kul[m]:=l;
  end;
  close(fi);
  sort(kul);
  if (n mod 2 = 0) then r:=n div 2
  else r:=(n+1) div 2;
  if (k mod 2 = 0) then
  for p:=r to (k div 2+r) do begin
  kyl[z]:=kul[r-1];
  kyl[z]:=kul[r+1];
  z:=z+2;
  end;
  sort(kyl);
  d:=kyl[1000]-kyl[1000-k];
  assign(fo,fout);
  rewrite(fo);
  write(fo,d);
  close(fo);
end.