#include <iostream>
#include <limits>
#include <queue>
#include <vector>

constexpr long long neg_inf = std::numeric_limits<long long>::min() / 2;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    std::size_t n, k;
    std::cin >> n >> k;

    std::vector<long long> a(n);
    for (auto &e : a) std::cin >> e;

    std::vector<long long> pd(k + 1, neg_inf);
    pd[1] = a[0];

    for (std::size_t i = 1; i < n; ++i) {
        std::vector<long long> dp(k + 1, neg_inf);
        dp[0] = pd[0];
        for (std::size_t j = 1; j <= k; ++j) {
            dp[j] = std::max(dp[j], pd[j] + a[i] * static_cast<long long>(j));
            if (j < k) {
                dp[j + 1] = std::max(dp[j + 1], pd[j] + a[i] * static_cast<long long>(j + 1));
            } else {
                dp[0] = std::max(dp[0], pd[k]);
            }
        }
        pd.swap(dp);
    }
    std::cout << std::max(pd[0], pd[k]) << std::endl;

    return 0;
}