#include <bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define vi vector<int>
#define ff first
#define ss second
#define all(x) x.begin(),x.end()
#define sp << " " <<
using namespace std;
const int N = 1e4+1,MOD = 1e9+7,inf = 2e18;
void solve() {
int n,k;
cin >> n >> k;
vi a(n+1);
for (int i=1;i<=n;i++) cin >> a[i];
//maximal penalty such that taker >= k
auto k_loose = [&](int lamb) -> pii {
pii dp[n+1][2];
dp[0][0] = {0,0};
for (int i=1;i<=n;i++) {
//ya yeni açıcam ya almicam ya devam ettircem
dp[i][0] = max(dp[i-1][0],dp[i-1][1]);
dp[i][1] = max(pii{dp[i-1][1].ff+a[i],dp[i-1][1].ss},pii{dp[i-1][0].ff+a[i]-lamb,dp[i-1][0].ss+1});
dp[i][1] = max(dp[i][1],pii{dp[i-1][1].ff+a[i]-lamb,dp[i-1][1].ss+1});
}
return max(dp[n][0],dp[n][1]);
};
int l = -1e15;
int r = 1e15;
while (l<=r) {
int m = (l+r) >> 1;
pii res = k_loose(m);
if (res.ss >= k) l = m+1;
else r = m-1;
}
pii res = k_loose(r);
cout << max(0ll,res.ff+r*k) << '\n';
};
signed main() {
ios_base::sync_with_stdio(0);cin.tie(0);
#ifdef Dodi
freopen("in.txt","r",stdin);
freopen("out.txt","w",stdout);
#endif
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
