#ifndef LOCAL
#define FAST_IO
#endif

// ============
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#define OVERRIDE(a, b, c, d, ...) d
#define REP2(i, n) for (i32 i = 0; i < (i32) (n); ++i)
#define REP3(i, m, n) for (i32 i = (i32) (m); i < (i32) (n); ++i)
#define REP(...) OVERRIDE(__VA_ARGS__, REP3, REP2)(__VA_ARGS__)
#define PER(i, n) for (i32 i = (i32) (n) - 1; i >= 0; --i)
#define ALL(x) begin(x), end(x)

using namespace std;

using u32 = unsigned int;
using u64 = unsigned long long;
using u128 = __uint128_t;
using i32 = signed int;
using i64 = signed long long;
using i128 = __int128_t;
using f64 = double;
using f80 = long double;

template <typename T>
using Vec = vector<T>;

template <typename T>
bool chmin(T &x, const T &y) {
    if (x > y) {
        x = y;
        return true;
    }
    return false;
}
template <typename T>
bool chmax(T &x, const T &y) {
    if (x < y) {
        x = y;
        return true;
    }
    return false;
}

istream &operator>>(istream &is, i128 &x) {
    i64 v;
    is >> v;
    x = v;
    return is;
}
ostream &operator<<(ostream &os, i128 x) {
    os << (i64) x;
    return os;
}
istream &operator>>(istream &is, u128 &x) {
    u64 v;
    is >> v;
    x = v;
    return is;
}
ostream &operator<<(ostream &os, u128 x) {
    os << (u64) x;
    return os;
}

[[maybe_unused]] constexpr i32 INF = 1000000100;
[[maybe_unused]] constexpr i64 INF64 = 3000000000000000100;
struct SetUpIO {
    SetUpIO() {
#ifdef FAST_IO
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
#endif
        cout << fixed << setprecision(15);
    }
} set_up_io;
// ============

#ifdef DEBUGF
#else
#define DBG(x) (void) 0
#endif

struct SlideMax {
    Vec<pair<i64, i32>> data;
    i32 l, r, it;
    
    SlideMax() : data(), l(0), r(0), it(0) {}
    
    void push(i64 val) {
        while (!data.empty() && data.back().first <= val) {
            data.pop_back();
        }
        data.emplace_back(val, r++);
    }
    
    void pop() {
        if (data[it].second == l) {
            ++it;
        }
        ++l;
    }
    
    i64 max() const {
        return data[it].first;
    }
    
    i32 size() const {
        return r - l;
    }
};

int main() {
    i32 n, k;
    cin >> n >> k;
    Vec<i64> a(n);
    REP(i, n) {
        cin >> a[i];
    }
    Vec<i64> sum(n + 1, 0);
    REP(i, n) {
        sum[i + 1] = sum[i] + a[i];
    }
    Vec<i64> dp(n + 1, 0);
    SlideMax mx;
    mx.push(-sum[1]);
    REP(i, 1, n + 1) {
        dp[i] = dp[i - 1];
        if (i < k) {
            chmax(dp[i], sum[i]);
        }
        chmax(dp[i], mx.max() + sum[i]);
        if (i != n) {
            mx.push(dp[i] - sum[i + 1]);
            if (mx.size() > k) {
                mx.pop();
            }
        }
    }
    cout << dp[n] << '\n';
}