#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n, k;
  cin >> n >> k;
  vector<long long> a(n);
  REP (i, n) cin >> a[i];
  sort(a.begin(), a.end());
  
  long long sum = a.back() - a.front();
  if (n > 1) {
    vector<long long> diff(n-1);
    for (int i = 1; i < n; i++)
      diff[i-1] = a[i] - a[i-1];
    sort(diff.begin(), diff.end());
    REP (i, k-1)
      sum -= diff[n-2-i];
  }
  cout << sum << endl;
  
  return 0;
}