program xxxx;
var n,k,p,w:longint;
    a:array[1..100000] of longint;

procedure paixu(l,r:longint);
var i,j,mid,temp:longint;
begin
  i:=l;
  j:=r;
  mid:=a[l+random(r-l+1)];
  repeat
    while a[i]<mid do
      inc(i);
    while mid<a[j] do
      dec(j);
    if i<=j then
      begin
        temp:=a[i];
        a[i]:=a[j];
        a[j]:=temp;
        inc(i);
        dec(j);
      end;
  until i>j;
  if l<j then
    paixu(l,j);
  if i<r then
    paixu(i,r);
end;


begin
  assign(input,'chess.in');
  reset(input);
  assign(output,'chess.out');
  rewrite(output);
  read(n,k);
  for p:=1 to n do
    read(a[p]);
  paixu(1,n);
  for p:=1 to n-1 do
    a[p]:=a[p+1]-a[p];
  paixu(1,n-1);
  w:=0;
  for p:=1 to k do
    w:=w+a[p];
  write(w);
  close(input);
  close(output);
end.