#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
int main()
{
// ifstream cin("input.txt");
// ofstream cout("output.txt");
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n, k; cin >> n >> k;
vector<ll> a(n), pref(n + 1, 0);
for (int i = 0; i < n; i++) {
cin >> a[i];
pref[i + 1] = pref[i] + a[i];
}
auto check = [&](ll lmb) {
pair<ll, ll> dp[n][2];
dp[0][0] = {0, 0};
dp[0][1] = {a[0] - lmb, 1};
for (int i = 1; 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 + a[i] - lmb, dp[i - 1][0].second + 1),
make_pair(dp[i - 1][1].first + a[i], dp[i - 1][1].second));
}
return max(dp[n - 1][0], dp[n - 1][1]);
};
ll lo = 0;
ll hi = 1e18;
while (lo < hi) {
ll mid = (lo + hi + 1) / 2;
check(mid).second >= k ? lo = mid : hi = mid - 1;
}
cout << check(lo).first + lo * k << endl;
}
