There are N squares aligned in a row. The i-th square from the left contains an integer a_i.

Initially, all the squares are white. Snuke will perform the following operation some number of times:

* Select K consecutive squares. Then, paint all of them white, or paint all of them black. Here, the colors of the squares are overwritten.



After Snuke finishes performing the operation, the score will be calculated as the sum of the integers contained in the black squares. Find the maximum possible score.

Constraints

* 1≤N≤10^5
* 1≤K≤N
* a_i is an integer.
* |a_i|≤10^9

Input

The input is given from Standard Input in the following format:


N K
a_1 a_2 ... a_N


Output

Print the maximum possible score.

Examples

Input

5 3
-10 10 -10 10 -10


Output

10


Input

4 2
10 -10 -10 10


Output

20


Input

1 1
-10


Output

0


Input

10 5
5 -4 -5 -8 -4 7 2 -4 0 7


Output

17
/*
URL https://
SCORE 0
AC false
WA false
TLE false
MLE false
TASK_TYPE
FAILURE_TYPE
NOTES
*/
#include <iostream>
#include <cstdint>
#include <utility>
#include <tuple>
#include <vector>
#include <stack>
#include <queue>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <set>
#include <algorithm>
#include <limits>
#include <numeric>
#include <iomanip>
#include <type_traits>
#include <functional>
#include <experimental/optional>

/* import STL */
// stream
using std::cout;
using std::cerr;
using std::cin;
using std::endl;
using std::flush;

// basic types
using std::nullptr_t;
using std::experimental::optional;
using std::pair;
using std::tuple;
using std::string;

// function for basic types
using std::experimental::make_optional;
using std::make_pair;
using std::make_tuple;
using std::get;

/* TODO remove them */
using std::vector;
using std::queue;
using std::stack;

// algorithms
using std::upper_bound;
using std::lower_bound;
using std::min_element;
using std::max_element;
using std::nth_element;
using std::accumulate;

/* macros */
// loops
#define REP(i, n) for (i64 i = 0; i < static_cast<decltype(i)>(n); ++i)
#define REPR(i, n) for (i64 i = (n) - 1; i >= static_cast<decltype(i)>(0); --i)
#define FOR(i, n, m) for (i64 i = (n); i < static_cast<decltype(i)>(m); ++i)
#define FORR(i, n, m) for (i64 i = (m) - 1; i >= static_cast<decltype(i)>(n); --i)
#define EACH(x, xs) for (auto &x: (xs))
#define EACH_V(x, xs) for (auto x: (xs))

// helpers
#define CTR(x) (x).begin(), (x).end()

/* utils for std::tuple */
namespace internal { namespace tuple_utils { // TODO rename to "internal::tuple"
    template<size_t...>
    struct seq {};

    template<size_t N, size_t... Is>
    struct gen_seq : gen_seq<N - 1, N - 1, Is...> {};

    template<size_t... Is>
    struct gen_seq<0, Is...> : seq<Is...> {};

    template<class Tuple, size_t... Is>
    void read(std::istream &stream, Tuple &t, seq<Is...>) {
        static_cast<void>((int[]) {0, (void(stream >> get<Is>(t)), 0)...});
    }

    template<class Tuple, size_t... Is>
    void print(std::ostream &stream, Tuple const &t, seq<Is...>) {
        static_cast<void>((int[]) {0, (void(stream << (Is == 0 ? "" : ", ") << get<Is>(t)), 0)...});
    }

    template<size_t I, class F, class A, class... Elems>
    struct ForEach {
        void operator()(A &arg, tuple<Elems...> const &t) const {
            F()(arg, get<I>(t));
            ForEach<I - 1, F, A, Elems...>()(arg, t);
        }

        void operator()(A &arg, tuple<Elems...> &t) const {
            F()(arg, get<I>(t));
            ForEach<I - 1, F, A, Elems...>()(arg, t);
        }
    };

    template<class F, class A, class... Elems>
    struct ForEach<0, F, A, Elems...> {
        void operator()(A &arg, tuple<Elems...> const &t) const {
            F()(arg, get<0>(t));
        }

        void operator()(A &arg, tuple<Elems...> &t) const {
            F()(arg, get<0>(t));
        }
    };

    template<class F, class A, class... Elems>
    void for_each(A &arg, tuple<Elems...> const &t) {
        ForEach<std::tuple_size<tuple<Elems...>>::value - 1, F, A, Elems...>()(arg, t);
    }

    template<class F, class A, class... Elems>
    void for_each(A &arg, tuple<Elems...> &t) {
        ForEach<std::tuple_size<tuple<Elems...>>::value - 1, F, A, Elems...>()(arg, t);
    }
}}

/* utils for Matrix (definition of Matrix) */
namespace internal { namespace matrix {
    template <typename V, int N>
    struct matrix_t {
        using type = std::vector<typename matrix_t<V, N-1>::type>;
    };
    template <typename V>
    struct matrix_t<V, 0> {
        using type = V;
    };

    template <typename V, int N>
    using Matrix = typename matrix_t<V, N>::type;

    template <typename V, typename It, int N>
    struct matrix_helper {
        static Matrix<V, N> create(const It &begin, const It &end, const V &default_value) {
            return Matrix<V, N>(*begin, matrix_helper<V, It, N - 1>::create(begin + 1, end, default_value));
        }
    };
    template <typename V, typename It>
    struct matrix_helper<V, It, 0> {
        static Matrix<V, 0> create(const It &begin __attribute__((unused)),
                                   const It &end __attribute__((unused)),
                                   const V &default_value) {
            return default_value;
        }
    };
}}

/* Primitive types */
using i8  =  int8_t; using  u8 =  uint8_t;
using i16 = int16_t; using u16 = uint16_t;
using i32 = int32_t; using u32 = uint32_t;
using i64 = int64_t; using u64 = uint64_t;
using usize = size_t;

/* Data structure type */
template <typename T> using Vector = std::vector<T>;
template <typename V> using OrderedSet = std::set<V>;
template <typename V> using HashSet = std::unordered_set<V>;
template <typename K, typename V> using OrderedMap = std::map<K, V>;
template <typename K, typename V> using HashMap = std::unordered_map<K, V>;
template <typename T, int N> using Matrix = internal::matrix::Matrix<T, N>;
template <typename T, typename Compare = std::less<T>, typename Container = std::vector<T>>
using PriorityQueue = std::priority_queue<T, Container, Compare>;

/* utils for Vector */
template <typename V>
Vector<V> make_pre_allocated_vector(size_t N) {
    Vector<V> retval;
    retval.reserve(N);
    return retval;
}

/* utils for Matrix */
template <class V, int N>
Matrix<V, N> make_matrix(const std::array<size_t, N> &shape, V default_value = V()) {
    return internal::matrix::matrix_helper<V, decltype(shape.begin()), N>::create(shape.begin(), shape.end(), default_value);
}

/* utils for STL iterators */
namespace internal {
    template <typename Iterator, typename F>
    struct MappedIterator {
        MappedIterator(const Iterator &it, const F &function) : it(it), function(function) {}
        auto operator *() const {
            return this->function(this->it);
        }
        void operator++() { ++this->it; }
        void operator+=(size_t n) { this->it += n; }
        auto operator+(size_t n) const {
            return MappedIterator<Iterator, F>(this->it + n, this->function);
        }
        bool operator==(const MappedIterator<Iterator, F> &rhs) const {
            return this->it == rhs.it;
        }
        bool operator!=(const MappedIterator<Iterator, F> &rhs) const {
            return !(*this == rhs);
        }
    private:
        Iterator it;
        F function;
    };
    template <typename Iterator, typename P>
    struct FilteredIterator {
        FilteredIterator(const Iterator &it, const Iterator &end, const P &predicate)
                : it(it), end(end), predicate(predicate) {
            if (this->it != end) {
                if (!predicate(this->it)) {
                    this->increment();
                }
            }
        }
        decltype(auto) operator *() const {
            return *this->it;
        }
        auto operator ->() const {
            return this->it;
        }
        void operator++() {
            this->increment();
        }
        void operator+=(size_t n) {
            REP (i, n) {
                this->increment();
            }
        }
        auto operator+(size_t n) const {
            auto retval = *this;
            retval += n;
            return retval;
        }
        bool operator==(const FilteredIterator<Iterator, P> &rhs) const {
            return this->it == rhs.it;
        }
        bool operator!=(const FilteredIterator<Iterator, P> &rhs) const {
            return !(*this == rhs);
        }
    private:
        void increment() {
            if (this->it == this->end) {
                return ;
            }
            ++this->it;
            while (this->it != this->end && !this->predicate(this->it)) {
                ++this->it;
            }
        }
        Iterator it;
        Iterator end;
        P predicate;
    };
    template <typename Iterator, typename ElementIterator>
    struct FlattenedIterator {
        FlattenedIterator(const Iterator &it, const Iterator &end) : it(make_pair(it, ElementIterator())), end(end) {
            if (this->it.first != this->end) {
                this->it.second = it->begin();
            }
            this->find_valid();
        }
        decltype(auto) operator *() const {
            return this->it;
        }
        const pair<Iterator, ElementIterator> *operator ->() const {
            return &this->it;
        }
        void operator++() {
            this->increment();
        }
        void operator+=(size_t n) {
            REP (i, n) {
                this->increment();
            }
        }
        auto operator+(size_t n) const {
            auto retval = *this;
            retval += n;
            return retval;
        }
        bool operator==(const FlattenedIterator<Iterator, ElementIterator> &rhs) const {
            if (this->it.first != rhs.it.first) {
                return false;
            }
            if (this->it.first == this->end || rhs.it.first == rhs.end) {
                if (this->end == rhs.end) {
                    return true;
                } else {
                    return false;
                }
            } else {
                return this->it.second == rhs.it.second;
            }
        }
        bool operator!=(const FlattenedIterator<Iterator, ElementIterator> &rhs) const {
            return !(*this == rhs);
        }
    private:
        bool is_end() const {
            return this->it.first == this->end;
        }
        bool is_valid() const {
            if (this->is_end()) return false;
            if (this->it.second == this->it.first->end()) return false;
            return true;
        }
        void _increment() {
            if (this->it.second == this->it.first->end()) {
                ++this->it.first;
                if (this->it.first != this->end) {
                    this->it.second = this->it.first->begin();
                }
            } else {
                ++this->it.second;
            }
        }
        void find_valid() {
            while (!this->is_end() && !this->is_valid()) {
                this->_increment();
            }
        }
        void increment() {
            this->_increment();
            while (!this->is_end() && !this->is_valid()) {
                this->_increment();
            }

        }
        pair<Iterator, ElementIterator> it;
        Iterator end;
    };
}

template <class Iterator>
struct Container {
    Container(const Iterator &begin, const Iterator &end) : m_begin(begin), m_end(end) {}
    const Iterator& begin() const {
        return this->m_begin;
    }
    const Iterator& end() const {
        return this->m_end;
    }
    Iterator m_begin;
    Iterator m_end;
};

template <typename C, typename F>
auto iterator_map(const C &c, F function) {
    using Iterator = std::remove_const_t<std::remove_reference_t<decltype(c.begin())>>;
    return Container<internal::MappedIterator<Iterator, F>>(
            internal::MappedIterator<Iterator, F>(c.begin(), function),
            internal::MappedIterator<Iterator, F>(c.end(), function));
}

template <typename C, typename P>
auto iterator_filter(const C &c, P predicate) {
    using Iterator = std::remove_const_t<std::remove_reference_t<decltype(c.begin())>>;
    return Container<internal::FilteredIterator<Iterator, P>>(
            internal::FilteredIterator<Iterator, P>(c.begin(), c.end(), predicate),
            internal::FilteredIterator<Iterator, P>(c.end(), c.end(), predicate));
}

template <typename C>
auto iterator_flatten(const C &c) {
    using Iterator = std::remove_const_t<std::remove_reference_t<decltype(c.begin())>>;
    using ElementIterator = std::remove_const_t<std::remove_reference_t<decltype(c.begin()->begin())>>;
    return Container<internal::FlattenedIterator<Iterator, ElementIterator>>(
            internal::FlattenedIterator<Iterator, ElementIterator>(c.begin(), c.end()),
            internal::FlattenedIterator<Iterator, ElementIterator>(c.end(), c.end()));
}

/* input */
template <class F, class S>
std::istream &operator>>(std::istream &stream, pair<F, S> &pair) {
    stream >> pair.first;
    stream >> pair.second;
    return stream;
}
template <class ...Args>
std::istream &operator>>(std::istream &stream, tuple<Args...> &tuple) {
    internal::tuple_utils::read(stream, tuple, internal::tuple_utils::gen_seq<sizeof...(Args)>());
    return stream;
}

template <class T>
T read() {
    T t;
    cin >> t;
    return t;
}
template <class F, class S>
pair<F, S> read() {
    pair<F, S> p;
    cin >> p;
    return p;
}
template <class T1, class T2, class T3, class ...Args>
tuple<T1, T2, T3, Args...> read() {
    tuple<T1, T2, T3, Args...> t;
    cin >> t;
    return t;
}
template <typename T, typename F = std::function<T()>>
Vector<T> read(const usize length, F r) {
    auto retval = make_pre_allocated_vector<T>(length);
    REP (i, length) {
        retval.emplace_back(r());
    }
    return retval;
}

template <class T>
Vector<T> read(const usize length) {
    return read<T>(length, [] { return read<T>(); });
}
template <class F, class S>
Vector<pair<F, S>> read(const usize length) {
    return read<pair<F, S>>(length);
}
template <class T1, class T2, class T3, class ...Args>
Vector<tuple<T1, T2, T3, Args...>> read(const usize length) {
    return read<tuple<T1, T2, T3, Args...>>(length);
}

namespace internal {
    template <typename T>
    struct oneline {
        std::string operator()(const T &t) const {
            std::ostringstream oss;
            oss << t;
            return oss.str();
        }
    };
    template <typename F, typename S>
    struct oneline<pair<F, S>> {
        std::string operator()(const pair<F, S> &p) const {
            std::ostringstream oss;
            oss << "{" << oneline<F>()(p.first) << ", " << oneline<S>()(p.second) << "}";
            return oss.str();
        }
    };
    template <typename ...Args>
    struct oneline<tuple<Args...>> {
        struct oneline_tuple {
            template<class V>
            void operator()(Vector<std::string> &strs, const V &v) const {
                strs.emplace_back(oneline<V>()(v));
            }
        };
        std::string operator()(const tuple<Args...> &t) const {
            std::ostringstream oss;
            Vector<std::string> strs;
            internal::tuple_utils::for_each<oneline_tuple, Vector<std::string>, Args...>(strs, t);
            oss << "{";
            REPR (i, strs.size()) {
                oss << strs[i];
                if (i != 0) {
                    oss << ", ";
                }
            }
            oss << "}";
            return oss.str();
        }
    };
    template <>
    struct oneline<bool> {
        std::string operator()(const bool b) const {
            return b ? "true" : "false";
        }
    };
    template <typename X>
    struct oneline<Vector<X>> {
        std::string operator()(const Vector<X> &vec) const {
            std::string retval = "[";
            auto f = oneline<X>();
            REP (i, vec.size()) {
                retval += f(vec[i]);
                if (i != static_cast<i64>(vec.size() - 1)) {
                    retval += ", ";
                }
            }
            retval += "]";
            return retval;
        }
    };
    template <typename X>
    struct oneline<OrderedSet<X>> {
        std::string operator()(const OrderedSet<X> &s) const {
            std::string retval = "{";
            auto f = oneline<X>();
            size_t ctr = 0;
            EACH (x, s) {
                retval += f(x);
                ctr += 1;
                if (ctr != s.size()) {
                    retval += ", ";
                }
            }
            retval += "}";
            return retval;
        }
    };
    template <typename X>
    struct oneline<HashSet<X>> {
        std::string operator()(const HashSet<X> &s) const {
            std::string retval = "{";
            auto f = oneline<X>();
            size_t ctr = 0;
            EACH (x, s) {
                retval += f(x);
                ctr += 1;
                if (ctr != s.size()) {
                    retval += ", ";
                }
            }
            retval += "}";
            return retval;
        }
    };
    template <typename K, typename V>
    struct oneline<OrderedMap<K, V>> {
        std::string operator()(const OrderedMap<K, V> &s) const {
            std::string retval = "{";
            auto f1 = oneline<K>();
            auto f2 = oneline<V>();
            size_t ctr = 0;
            EACH (x, s) {
                retval += f1(x.first);
                retval += ": ";
                retval += f2(x.second);
                ctr += 1;
                if (ctr != s.size()) {
                    retval += ", ";
                }
            }
            retval += "}";
            return retval;
        }
    };
    template <typename K, typename V>
    struct oneline<HashMap<K, V>> {
        std::string operator()(const HashMap<K,V> &s) const {
            std::string retval = "{";
            auto f1 = oneline<K>();
            auto f2 = oneline<V>();
            size_t ctr = 0;
            EACH (x, s) {
                retval += f1(x.first);
                retval += ": ";
                retval += f2(x.second);
                ctr += 1;
                if (ctr != s.size()) {
                    retval += ", ";
                }
            }
            retval += "}";
            return retval;
        }
    };

    template <typename V>
    struct keys { /* no implementation */ };
    template <typename X>
    struct keys<std::vector<X>> {
        Vector<size_t> operator()(const Vector<X> &v) const {
            Vector<size_t> keys;
            REP (i, v.size()) {
                keys.emplace_back(i);
            }
            return keys;
        }
    };
    template <typename K, typename V>
    struct keys<OrderedMap<K, V>> {
        Vector<K> operator()(const OrderedMap<K, V> &c) const {
            Vector<K> keys;
            EACH (elem, c) {
                keys.emplace_back(elem.first);
            }
            return keys;
        }
    };
    template <typename K, typename V>
    struct keys<HashMap<K, V>> {
        Vector<K> operator()(const HashMap<K, V> &c) const {
            Vector<K> keys;
            EACH (elem, c) {
                keys.emplace_back(elem.first);
            }
            return keys;
        }
    };
}

template <typename T>
void dump(const T& t) {
    using namespace internal;
    std::cerr << oneline<T>()(t) << std::endl;
}
template <typename V1, typename V2, typename ...Args>
void dump(const V1 &v1, const V2 &v2, const Args&... args) {
    using namespace internal;
    using F = typename oneline<tuple<V1, V2, Args...>>::oneline_tuple;
    auto x = std::make_tuple(v1, v2, args...);
    Vector<std::string> strs;
    internal::tuple_utils::for_each<F, Vector<std::string>, V1, V2, Args...>(strs, x);
    REPR (i, strs.size()) {
        std::cerr << strs[i];
        if (i != 0) {
            std::cerr << ", ";
        }
    }
    std::cerr << std::endl;
}

template <typename C>
std::string as_set(const C& ctr) {
    Vector<std::string> values;

    using namespace internal;
    EACH (x, ctr) {
        values.emplace_back(oneline<decltype(x)>()(x));
    }
    std::string retval = "---\n";
    REP (i, values.size()) {
        retval += values[i];
        retval += "\n";
    }
    retval += "---";

    return retval;
}

template <typename C>
std::string as_map(const C& ctr) {
    using namespace internal;

    auto ks = keys<C>()(ctr);
    Vector<std::string> keys;
    Vector<std::string> values;

    EACH (key, ks) {
        keys.emplace_back(oneline<decltype(key)>()(key));
        values.emplace_back(oneline<decltype(ctr.at(key))>()(ctr.at(key)));
    }
    size_t l = 0;
    EACH (key, keys) {
        l = std::max(l, key.size());
    }
    std::string retval = "---\n";
    REP (i, values.size()) {
        retval += keys[i];
        REP (j, l - keys[i].size()) {
            retval += " ";
        }
        retval += ": ";
        retval += values[i];
        retval += "\n";
    }
    retval += "---";

    return retval;
}

template <typename C>
std::string as_table(const C &ctr) {
    using namespace internal;
    auto rkeys = keys<C>()(ctr);
    auto ckeys = OrderedSet<std::string>();

    auto values = Vector<pair<std::string, OrderedMap<std::string, std::string>>>();

    /* Stringify all data */
    EACH (rkey, rkeys) {
        auto rkey_str = oneline<decltype(rkey)>()(rkey);
        values.emplace_back(rkey_str, OrderedMap<std::string, std::string>());

        auto row = ctr.at(rkey);
        auto ks = keys<decltype(row)>()(row);
        EACH (ckey, ks) {
            auto ckey_str = oneline<decltype(ckey)>()(ckey);
            ckeys.emplace(ckey_str);
            values.back().second.emplace(ckey_str, oneline<decltype(row.at(ckey))>()(row.at(ckey)));
        }
    }

    /* Calculate string length */
    size_t max_row_key_length = 0;
    EACH (value, values) {
        max_row_key_length = std::max(max_row_key_length, value.first.size());
    }

    OrderedMap<std::string, size_t> max_col_length;
    EACH (ckey, ckeys) {
        max_col_length.emplace(ckey, ckey.size());
    }

    EACH (value, values) {
        EACH (elem, value.second) {
            auto ckey = elem.first;
            auto value = elem.second;
            max_col_length[ckey] = std::max(max_col_length[ckey], value.size());
        }
    }

    std::string retval = "---\n";
    /* Header */
    REP(i, max_row_key_length) {
        retval += " ";
    }
    retval += "  ";
    size_t cnt = 0;
    EACH (ckey, ckeys) {
        retval += ckey;
        REP (j, max_col_length[ckey] - ckey.size()) {
            retval += " ";
        }

        cnt += 1;
        if (cnt != ckeys.size()) {
            retval += ", ";
        }
    }
    retval += "\n------\n";

    /* Values */
    EACH (value, values) {
        retval += value.first;
        REP(i, max_row_key_length - value.first.size()) {
            retval += " ";
        }
        retval += "| ";

        size_t cnt = 0;
        EACH (ckey, ckeys) {
            auto v = std::string("");
            if (value.second.find(ckey) != value.second.end()) {
                v = value.second.at(ckey);
            }
            retval += v;
            REP (j, max_col_length[ckey] - v.size()) {
                retval += " ";
            }

            cnt += 1;
            if (cnt != ckeys.size()) {
                retval += ", ";
            }

        }

        retval += "\n";
    }
    retval += "---";
    return retval;
}


// Hash
namespace std {
    template <class F, class S>
    struct hash<pair<F, S>> {
        size_t operator ()(const pair<F, S> &p) const {
            return hash<F>()(p.first) ^ hash<S>()(p.second);
        }
    };

    template <class ...Args>
    struct hash<tuple<Args...>> {
        struct hash_for_element {
            template<class V>
            void operator()(size_t &size, const V &v) const {
                size ^= std::hash<V>()(v);
            }
        };

        size_t operator ()(const tuple<Args...> &t) const {
            size_t retval = 0;

            internal::tuple_utils::for_each<hash_for_element, size_t, Args...>(retval, t);

            return retval;
        }
    };
}
#define MAIN
void body();

// main function (DO NOT EDIT)
int main (int argc, char **argv) {
    cin.tie(0);
    std::ios_base::sync_with_stdio(false);

    cout << std::fixed;
    body();

    return 0;
}

void body() {
    auto N = read<i64>();
    auto K = read<i64>();
    auto as = read<i64>(N);

    i64 all_positive_numbers = 0;
    EACH (a, as) {
        if (a < 0) continue;
        all_positive_numbers += a;
    }

    i64 pmin_white_K = 0;
    i64 max_black_K = 0;
    i64 pmax_black_K = 0;
    REP (i, K) {
        pmin_white_K += std::max(0L, as[i]);
        pmax_black_K += std::max(0L, as[i]);
        max_black_K += as[i];
    }
    i64 pmin = pmin_white_K, pmax = pmax_black_K, m = max_black_K;
    FOR (i, 1, N - K + 1) {
        auto t = pmin;
        t -= std::max(0L, as[i - 1]);
        t += std::max(0L, as[i + K - 1]);
        if (t < pmin_white_K) {
            pmin_white_K = t;
        }
        auto s1 = pmax;
        s1 -= std::max(0L, as[i - 1]);
        s1 += std::max(0L, as[i + K - 1]);

        auto s2 = m;
        s2 -= as[i - 1];
        s2 += as[i + K - 1];
        if (s2 > max_black_K) {
            max_black_K = s2;
            pmax_black_K = s1;
        }

        pmin = t;
        pmax = s1;
        m = s2;
    }

    auto c1 = all_positive_numbers - pmin_white_K;
    auto c2 = all_positive_numbers - pmax_black_K + max_black_K;
    cout << std::max(c1, c2) << endl;
}
