#include <algorithm>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>

using namespace std;

typedef long long ll;

#define MOD 1000000007

int main() {
  int n, k;
  cin >> n >> k;
  vector<ll> a(n);
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
  }
  sort(a.begin(), a.end());
  vector<ll> sub;
  for (int i = 0; i + 1 < n; ++i) {
    sub.push_back(a[i + 1] - a[i]);
  }
  sort(sub.begin(), sub.end());
  k = k - 1;
  while (k--) {
    sub.pop_back();
  }
  ll ans = accumulate(sub.begin(), sub.end(), 0ll);
  cout << ans << endl;
  return 0;
}