#!/usr/bin/env perl

use strict;
use warnings;

my ($n, $k) = split / /, <>; chomp $k;
my @array = split / /, <>;
chomp $array[$n - 1];

@array = sort { $a <=> $b } @array;
my @narray;
for (my $i = 0; $i < $n - 1; $i++) {
  push @narray, $array[$i + 1] - $array[$i];
}

@narray = sort { $a <=> $b } @narray;
my $res = 0;
for (my $i = 0; $i < $n - $k; $i++) {
  $res += $narray[$i];
}

print $res, "\n";