program Project1;

{$APPTYPE CONSOLE}
var
  f:text;
  a,b, c:int64;
  s:array[1..100000] of int64;

procedure sort(l,r:int64);
var
  x,a,b,y:int64;
begin
  x:=s[(l+r) div 2];
  a:=l;
  b:=r;
  while a<b do begin
  while x>s[a] do inc(a);
  while x<s[b] do dec(b);
    y:=s[a];
    s[a]:=s[b];
    s[b]:=y;
    inc(a);
    dec(b);
  end;
  if a>l then sort(l, a);
  if b<r then sort (b, r);
end;
begin
assign(f, 'holy.in');
reset(f);
readln(f, a, b);
c:=0;
repeat
inc(c);
read(f, s[c]);
until (c=a);
sort(1, a);
c:=s[b]-s[1];
assign(f, 'holy.out');
rewrite(f);
writeln(f, c);
close(f);
end.