program ct1;

{$APPTYPE CONSOLE}
var
  f:text;
  a,b, c:int64;
  s:array[1..100000] of int64;
procedure sort;
var x, z ,y, n, m:int64;
begin
  z:=0;
  repeat
  inc(z);
  y:=z;
  n:=z;
  repeat
  inc(y);
  if s[n]>s[y] then n:=y;
  until (y=a);
  y:=s[z];
  s[z]:=s[n];
  s[n]:=y;
  until (z=a-1);

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;
c:=s[b]-s[1];
assign(f, 'holy.out');
rewrite(f);
writeln(f, c);
close(f);
end.