// author : MOHAMMED OMAR FAIAZ ONIM
// gmail : u2104029@student.cuet.ac.bd
// 戦え
#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
const int N = 2e5 + 5;
const long long INF = 1e18;
#define ll long long
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int testcases = 1;
// cin>>testcases;
while (testcases--)
{
ll n, k;
cin >> n >> k;
vector<ll> v(n);
vector<ll> comp;
for (ll i = 0; i < n; i++)
{
cin >> v[i];
}
ll sum = 0, l = 0, ok = 1;
vector<ll> neg;
vector<ll> poscomp;
ll sz = 0;
while (l < n)
{
if (ok)
{
while (ok && l < n && v[l] >= 0)
{
sz++;
sum += v[l];
l++;
}
comp.push_back(sum);
poscomp.push_back(sum);
}
else
{
while (!ok && l < n && v[l] < 0)
{
neg.push_back(v[l]);
sum += v[l];
l++;
}
comp.push_back(sum);
}
sum = 0;
ok ^= 1;
}
if (k >= poscomp.size())
{
ll ans = accumulate(poscomp.begin(), poscomp.end(), 0ll);
ll rem = max(k - sz, 0ll);
sort(neg.begin(), neg.end());
while (rem--)
{
ans += neg.back();
neg.pop_back();
}
cout << ans << "\n";
return 0;
}
// sz = poscomp.size();
// cout<<sz<<endl;
ll y = 20;
while (y--)
{
for (ll i = 0; i < comp.size(); i++)
{
if (comp[i] < 0 && i - 1 >= 0 && i + 1 < comp.size() && (comp[i - 1] + comp[i + 1] + comp[i]) > max(comp[i - 1], comp[i+1]))
{
// cout<<comp[i-1]<<" "<<comp[i]<<" "<<comp[i+1]<<" "<<endl;
comp[i + 1] = comp[i - 1] + comp[i + 1] + comp[i];
comp[i - 1] = 0;
comp[i] = 0;
// cout<<"ok"<<endl;
}
}
// for (auto &to : comp)
// cout << to << " ";
// cout << endl;
vector<ll> v;
for (auto &i : comp)
{
if (i != 0)
v.push_back(i);
}
comp = v;
for (ll i = comp.size() - 1; i >= 0; i--)
{
if (comp[i] < 0 && i - 1 >= 0 && i + 1 < comp.size() && (comp[i - 1] + comp[i + 1] + comp[i]) > max(comp[i - 1], comp[i+1]))
{
comp[i + 1] = 0;
comp[i] = 0;
comp[i - 1] = comp[i - 1] + comp[i + 1] + comp[i];
}
}
v.clear();
for (auto &i : comp)
{
if (i != 0)
v.push_back(i);
}
comp = v;
}
sort(comp.begin(), comp.end());
ll ans = 0;
while (k--)
{
ans += comp.back();
comp.pop_back();
}
cout << ans << endl;
}
}
