#include <bits/stdc++.h>
using namespace std;

#define rep(i, l, r) for (int i = (int)(l); i<(int)(r); i++)
#define ll long long

int K;

template<class T>
struct TopK {
    ll sum;
    priority_queue<T, vector<T>, greater<T>> ms;
    TopK() {
        sum = 0;
    }
    void insert(T x) {
        if ((int)ms.size() < K-1) {
            ms.push(x);
            sum += x;
        }
        else {
            if (ms.top() < x) {
                sum -= ms.top();
                ms.pop();
                sum += x;
                ms.push(x);
            }
        }
    }
};

int main() {
    //dp[i][j] = i までで取り除いたpref = j
    //dp[i][j] = max(dp[i-1][k] + (S[j]-S[i])*i) (k < j)
    //dp[i][j] = max(dp[i-1][k]-S[k]*i + S[j]*i)
    
    //A[0]*1, A[1]*1, A[2]*2, A[2]*2 ...
    //A[0:] + A[2:] + A[x:]
    //dp[i][j] = i: で、すでにj個使ったときの場合の数

    int N; cin >> N >> K;
    vector<ll> A(N);
    rep(i, 0, N) cin >> A[i];
    if (K == 1) {
        ll now = 0;
        ll ans = -4e18;
        for (int i = 0; i < N; i++) {
            now += A[i];
            ans = max(ans, now);
        }
        cout << ans << endl;
        return 0;
    }
    vector<ll> S(N+1);
    S[N] = 0;
    for (int i = N-1; i >= 0; i--) {
        S[i] = S[i+1] + A[i];
    }
    ll ans = -4e18;
    TopK<ll> T;
    rep(i, 1, K) T.insert(S[i]);
    // for (auto v : S) cout << v << " ";
    // cout << endl;
    for (int last = K; last <= N; last++) {
        ll x = T.sum + S[0];
        // cout << "last = "<< last << endl << x << " : " << S[last] << " : " << x - S[last]*K << endl;
        ans = max(ans, x - S[last] * K);
        if (last != N) {
            T.insert(S[last]);
        }
    }
    cout << ans << endl;
}