/*For today, you happen to be the defeated. But what will you become tomorrow?*/
#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 300005;
const ll inf = (1ll << 60);
int arr[N], n, k;
array<ll, 2> dp[N][2];
array<ll, 2> f(ll c) {
for(int i = 0; i <= n; i ++) {
dp[i][0] = {0, 0};
dp[i][1] = {-inf, 0};
}
for(int i = 1; i <= n; i ++) {
dp[i][0] = dp[i - 1][0];
dp[i][1] = {dp[i - 1][1][0] + (ll)arr[i], dp[i - 1][1][1]};
array<ll, 2> cur = {dp[i - 1][0][0] + (ll)arr[i] - c, dp[i - 1][0][1] + 1};
dp[i][1] = max(dp[i][1], cur);
dp[i][0] = max(dp[i][0], dp[i][1]);
}
return dp[n][0];
}
void solve() {
cin >> n >> k;
for(int i = 1; i <= n; i ++) cin >> arr[i];
ll lo = 0, hi = (1ll << 60), ans = 0;
while(lo <= hi) {
ll mid = (lo + hi) / 2;
array<ll, 2> yo = f(mid);
if(yo[1] >= k) {
ans = yo[0] + k * mid;
lo = mid + 1;
}
else {
hi = mid - 1;
}
}
cout << ans << '\n';
}
int32_t main() {
ios::sync_with_stdio(0);
cin.tie(0);
int t = 1;
// cin >> t;
while(t--){
solve();
}
return 0;
}
