#include <bits/stdc++.h>
#include <math.h>

#include <algorithm>
#include <array>
#include <atcoder/all>
#include <bitset>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <sstream>
#include <vector>

using namespace std;
using namespace atcoder;

using Graph = vector<vector<int>>;

using ll = long long;
typedef pair<ll, ll> P_ll;
typedef pair<int, int> P;

const ll INF_ll = 1e17;
const int INF = 1e8;
template <class T>
bool chmax(T& a, const T& b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
bool chmin(T& a, const T& b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T>
using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;

int main() {
  ll N, K;
  cin >> N >> K;
  vector<ll> a(N);
  for (int i = 0; i < N; i++) {
    cin >> a[i];
  }
  sort(a.begin(), a.end());
  ll ans = 0;
  vector<ll> b;
  for (int i = 1; i < N; i++) {
    ans += a[i] - a[i - 1];
    b.push_back(a[i] - a[i - 1]);
  }
  sort(b.rbegin(), b.rend());
  for (int i = 0; i < K - 1; i++) {
    ans -= b[i];
  }
  cout << ans << endl;

  return 0;
}