#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
template <class T>
using V = vector<T>;
const ll inf = (1e18);
const ll mod = 1000000007;
ll GCD(ll a, ll b) { return b ? GCD(b, a % b) : a; }
ll LCM(ll c, ll d) { return c / GCD(c, d) * d; }
struct __INIT {
  __INIT() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
  }
} __init;
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 (a > b) {
    a = b;
    return 1;
  }
  return 0;
}
ll dp[2][300005];
int main() {
  ll n, k;
  cin >> n >> k;
  V<ll> a(n), sum(n + 1, 0);
  for (int i = 0; i < n; i++) cin >> a[i];
  reverse((a).begin(), (a).end());
  for (int i = 1; i < n; i++) a[i] += a[i - 1];
  ll ans = a[n - 1];
  a.pop_back();
  sort((a).begin(), (a).end());
  for (int i = n - 2; i > n - 1 - k; i--) {
    ans += a[i];
  }
  cout << ans << "\n";
}
