#include <bits/stdc++.h> // +
using namespace std; // +++
#define inf 1e18 // +
#define int long long
#define ll __int128_t
#define all(a) a.begin(), a.end()
int const N = 3e5 + 5;
pair<ll, ll> dp[N][2];
int vis[N][2], id;
int n, k, a[N];
ll lamda;
pair<ll, ll> rec(int i, bool lst) {
if (i == n) return {0, 0};
auto &ret = dp[i][lst];
if (vis[i][lst] == id) return ret;
vis[i][lst] = id;
auto leave = rec(i + 1, 0);
auto take = rec(i + 1, 1);
take.first += a[i];
if (!lst) {
take.first -= lamda;
take.second--;
}
return ret = max(leave, take);
}
void solve() {
cin >> n >> k;
for (int i = 0; i < n; ++i) cin >> a[i];
int st = 0, en = 1e15, md, ans = 0;
while (st <= en) {
md = (st + en) / 2;
lamda = md;
++id;
auto [d, cnt] = rec(0, 0);
ll used = -cnt;
if (used > k) st = md + 1;
else {
ans = (int)(d + lamda * k);
en = md - 1;
}
}
cout << ans << '\n';
}
signed main() {
ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
int tc = 1;
// cin >> tc;
while (tc--)
solve();
}
