#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "local_debug.cpp"
#else
#define debug(...)
#define debugArr(...)
#endif
#define int long long
#define nl '\n'
#define sp ' '
#define F first
#define S second
#define SZ(s) (int)((s).size())
const int N = 3e5 + 5;
int a[N];
void solve() {
int n, k; cin >> n >> k;
for(int i = 0; i < n; ++i) cin >> a[i];
auto solve = [&](const int lmb) {
pair <int, int> 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].F + a[i] - lmb, dp[i - 1][0].S + 1), make_pair(dp[i - 1][1].F + a[i], dp[i - 1][1].S));
}
return max(dp[n - 1][0], dp[n - 1][1]);
};
int l = 0, r = 1e18, mid, lmb_opt;
while(l <= r) {
mid = (l + r) >> 1;
if(solve(mid).S >= k) lmb_opt = mid, l = mid + 1;
else r = mid - 1;
}
cout << solve(lmb_opt).F + lmb_opt * solve(lmb_opt).S << nl;
}
signed main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr);
int tc = 1;
// cin >> tc;
while(tc--) solve();
}
