program chess(input,output);

type
  tlist=array[1..100000]of longint;

var
  n,k,i,j:longint;
  lv:tlist;

procedure qsort(var a:tlist; const max:longint);
  procedure sort(l,r: longint);
    var
      i,j,x,y: longint;
    begin
      i:=l;
      j:=r;
      x:=a[(l+r) div 2];

      repeat
        while a[i]<x do
          inc(i);

        while x<a[j] do
          dec(j);

        if not(i>j) then
        begin
          y:=a[i];
          a[i]:=a[j];
          a[j]:=y;
          inc(i);
          dec(j);
        end;
      until i>j;

      if l<j then
        sort(l,j);
      if i<r then
        sort(i,r);
    end;

  begin
    sort(1,max);
  end;

begin
  assign(input,'chess.in');
  reset(input);
  assign(output,'chess.out');
  rewrite(output);

  readln(n,k);
  for i:=1 to n do
    readln(lv[i]);

  qsort(lv,n);

  for i:=1 to n-1 do
    lv[i]:=lv[i+1]-lv[i];

  qsort(lv,n);

  n:=0;
  for i:=1 to k do
    n:=n+lv[i];

  writeln(n);

  close(input);
  close(output);
end.