/* -*- coding: utf-8 -*-
 *
 * 615.cc: No.615 集合に分けよう - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 50000;

/* typedef */

typedef long long ll;

/* global variables */

ll as[MAX_N], bs[MAX_N];

/* subroutines */

/* main */

int main() {
  int n, k;
  scanf("%d%d", &n, &k);

  for (int i = 0; i < n; i++) scanf("%lld", &as[i]);
  sort(as, as + n);

  for (int i = 0; i < n - 1; i++) bs[i] = as[i + 1] - as[i];
  sort(bs, bs + n - 1);

  ll sum = 0;
  for (int i = 0; i < k - 1; i++) sum += bs[n - 2 - i];

  printf("%lld\n", as[n - 1] - as[0] - sum);
  return 0;
}