#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int32_t main () {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int N, K;
cin >> N >> K;
vector<ll> arr(N + 1, 0);
for (int i = 1;i <= N;i ++) cin >> arr[i];
vector<vector<pair<ll, ll>>> dp(N + 1, {{0, 0}, {0, 0}});
auto calculate = [&](ll mid) -> void {
dp[1][0] = {0, 0};
dp[1][1] = {arr[1] - mid, 1};
for (int i = 2;i <= N;i ++) {
dp[i][0] = max(dp[i - 1][0], dp[i - 1][1]);
dp[i][1] = max(make_pair(dp[i - 1][0].first + arr[i] - mid, dp[i - 1][0].second + 1), make_pair(dp[i - 1][1].first + arr[i], dp[i - 1][1].second));
}
};
ll lo = 0, hi = 1e16 + 6789;
while (lo + 1 < hi) {
ll mid = (lo + hi) / 2LL;
calculate (mid);
if (max(dp[N][0], dp[N][1]).second < K) {
hi = mid;
} else {
lo = mid;
}
}
calculate (lo);
cout << max(dp[N][0], dp[N][1]).first + lo * K << "\n";
}
