#include <iostream>
constexpr long long INF = 1e18;
constexpr int MAX_N = 3e5 + 5;
int N, K, a[MAX_N];
std::pair<long long, int> dp[MAX_N][2];
std::pair<long long, int> check(long long lambda) {
dp[1][0] = { 0, 0 };
dp[1][1] = { a[1] - lambda, 1 };
for (int i = 2; i <= N; ++i) {
dp[i][0] = std::max(dp[i - 1][0], dp[i - 1][1]);
dp[i][1] = std::max(
std::make_pair(dp[i - 1][0].first + a[i] - lambda, dp[i - 1][0].second + 1),
std::make_pair(dp[i - 1][1].first + a[i], dp[i - 1][1].second)
);
}
return std::max(dp[N][0], dp[N][1]);
}
int32_t main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);
std::cin >> N >> K;
for (int i = 1; i <= N; ++i)
std::cin >> a[i];
long long l = 0, r = INF, ans = 0;
while (l <= r) {
long long mid = (l + r) >> 1;
std::pair<long long, int> res = check(mid);
if (res.second >= K) {
ans = res.first + mid * res.second;
l = mid + 1;
} else r = mid - 1;
}
std::cout << ans;
return 0;
}
