#include <bits/stdc++.h>
#define REP(i, a, n) for(ll i = ((ll) a); i < ((ll) n); i++)
using namespace std;
typedef long long ll;

int main(void) {
  ll N, K; cin >> N >> K;
  vector<ll> A(N);
  REP(i, 0, N) cin >> A[i];

  sort(A.begin(), A.end());

  vector<ll> diff(N - 1);
  REP(i, 0, N - 1) diff[i] = A[i + 1] - A[i];

  sort(diff.begin(), diff.end());

  ll ans = 0;
  REP(i, 0, N - K) ans += diff[i];
  cout << ans << endl;
}