#include <bits/stdc++.h>

using namespace std;

template<class F, class S>
ostream &operator<<(ostream &s, const pair<F, S> &v) {
    s << "(" << v.first << ", " << v.second << ")";
    return s;
}
template<ranges::range T> requires (!is_convertible_v<T, string_view>)
istream &operator>>(istream &s, T &&v) { 
    for (auto &&x : v) s >> x; 
    return s; 
}
template<ranges::range T> requires (!is_convertible_v<T, string_view>)
ostream &operator<<(ostream &s, T &&v) { 
    for (auto &&x : v) s << x << ' '; 
    return s; 
}

#ifdef LOCAL
template<class... T> void dbg(T... x) {
    char e{};
    ((cerr << e << x, e = ' '), ...);
}
#define debug(x...) dbg(#x, '=', x, '\n')
#else
#define debug(...) ((void)0)
#endif

#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define ff first
#define ss second

template<class T> inline constexpr T inf = numeric_limits<T>::max() / 2;
bool chmin(auto &a, auto b) { return (b < a and (a = b, true)); }
bool chmax(auto &a, auto b) { return (a < b and (a = b, true)); }

using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;
using i128 = __int128;
using u128 = unsigned __int128;

constexpr i64 mod = 998244353;

void solve() {
    int N, K;
    cin >> N >> K;

    vector<i64> A(N);
    cin >> A;

    for (int i = N - 2; i >= 0; i--) {
        A[i] += A[i + 1];
    }

    priority_queue<i64, vector<i64>, greater<i64>> pq;
    i64 sum = A[0];

    vector<i64> f(N, -inf<i64>);
    for (int i = 1; i < N; i++) {
        pq.push(A[i]);
        sum += A[i];
        while (pq.size() >= K) {
            sum -= pq.top();
            pq.pop();
        }
        f[i] = f[i - 1];
        if (pq.size() == K - 1) {
            f[i] = sum;
        }
    }

    i64 ans = -inf<i64>;
    for (int i = 0; i < N; i++) {
        chmax(ans, f[i] - K * (i + 1 == N ? 0 : A[i + 1]));
    }

    cout << ans << '\n';
}

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    int t = 1;
    // cin >> t;

    while (t--) {
        solve();
    }

    return 0;
}