#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
  #include "settings/debug.cpp"
#else
  #define Debug(...) void(0)
#endif
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int n, k;
  cin >> n >> k;
  vector<ll> a(n);
  rep(i, n) cin >> a[i];
  sort(a.begin(), a.end());
  vector<ll> b(n - 1);
  rep(i, n - 1) b[i] = a[i + 1] - a[i];
  sort(b.begin(), b.end());
  ll ans = 0;
  rep(i, n - k) ans += b[i];
  cout << ans << '\n';
  return 0;
}