program zadasha2;
var i,j,c:integer; min,n,k,maks,x,y:int64; d:array[1..100000] of integer; f1,f2:text;

begin
assign(f1,'holy.txt');
reset(f1);
read(f1,n); readln(f1,k);
for i:=1 to n do
read(f1,d[i]);
close(f1);
c:=0;
min:=9999999999;
maks:=0;
while c<k do

 begin

  for i:=1 to n do
   for j:=1 to n do
    begin
     if (d[i]-d[j]>0) and (d[i]-d[j]<min) and (d[i]-d[j]>maks) then
      min:=d[i]-d[j];
      x:=d[i]; y:=d[j];
     end;
    for i:=1 to n do

     if (d[i]<x) and (d[j]>y) then
      c:=c+1;
     maks:=min;

  end;
assign(f2,'holy.txt');
rewrite(f2);
writeln(f2,maks);
close(f2);


end.