program chess;
var
 a,ans:array [1..10000] of longint;
 n,k:longint;
 f1,f2:text;

procedure init;
var i:longint;
begin
 assign(f1,'chess.in'); reset(f1);
 assign(f2,'chess.out'); rewrite(f2);
 readln(f1,n,k);
 for i:=1 to n do
  readln(f1,a[i]);
 close(f1);
end;

procedure qsort(x,y:longint);
var l,r,k,temp:longint;
begin
 l:=x;
 r:=y;
 k:=a[(x+y) div 2];
 repeat
  while a[l]<k do inc(l);
  while a[r]>k do dec(r);
  if l<=r then begin
   temp:=a[l];
   a[l]:=a[r];
   a[r]:=temp;
   inc(l); dec(r);
  end;
 until l>r;
 if r>x then qsort(x,r);
 if l<y then qsort(l,y);
end;

procedure play;
var i,s:longint;
begin
 s:=0;
 qsort(1,n);
 for i:=1 to n-1 do
  a[i]:=a[i+1]-a[i];
 qsort(1,n-1);
 for i:=1 to k do
  s:=s+a[i];
 writeln(f2,s);
 close(f2);
end;

begin
 init;
 play;
end.