program Project2;

{$APPTYPE CONSOLE}

var n,k,min,i,j,p,max,ii:integer;
    a:array[1..100000]of integer;
begin
assign(Input,'holy.in');
reset(Input);
readln(n,k);
for i:=1 to n do read(a[i]);
close(Input);


for i:=1 to n do begin
  min:=1000000000;
  for j:=i to n do
  if a[j]<min then begin min:=a[j]; ii:=j; end;
  p:=a[i];
  a[i]:=a[ii];
  a[ii]:=p;
  end;

  //min:=1000000000; max:=-1;
  if (n-k) mod 2 =0 then
              begin
                  min:=a[((n-k)div 2)+1];
                  max:=a[n -((n-k) div 2)];
              end
                                    else
              
  if (a[n -((n-k) div 2)-1]-a[(n-k)div 2])<(a[n -((n-k) div 2)]-a[((n-k)div 2)+1]) then begin
                  min:=a[(n-k)div 2];
                  max:=a[n -((n-k) div 2)-1];
              end

              else  begin
                  min:=a[((n-k)div 2)+1];
                  max:=a[n -((n-k) div 2)];
              end   ;


  assign(Output,'holy.out');
  rewrite(Output);
  {for i:=1 to n do write(a[i],' ');   writeln;
  writeln(max);
  writeln(min);
  writeln('---'); }
  writeln(max-min);
  close(Output);
end.