#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
vector<ll> a, b;
ll res;
ll solve(ll pun)
{
res = 0;
ll last = -pun;
ll seg_cnt = 0;
for (auto n : b)
{
if (n > 0)
{
last += n;
continue;
}
if (n < -pun)
{
if (last > 0)
{
res += last;
seg_cnt++;
}
last = -pun;
}
else
{
last += n;
}
if (last < -pun)
last = -pun;
}
if (last > 0)
{
res += last;
seg_cnt++;
}
return seg_cnt;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
ll N, K;
cin >> N >> K;
for (int i = 0; i < N; i++)
{
ll n; cin >> n;
if (n != 0)
a.push_back(n);
}
N = a.size();
{
int i = 0;
while (i < N && a[i] < 0)
i++;
ll sum = 0;
if (i < N) sum = a[i];
for (i++; i < N; i++)
{
if ((a[i-1] ^ a[i]) < 0)
{
b.push_back(sum);
sum = 0;
}
sum += a[i];
}
if (sum != 0)
b.push_back(sum);
if (b.size() && b.back() <= 0)
b.pop_back();
}
if (b.size() == 0)
{
cout << 0 << '\n';
return 0;
}
ll l = 0ll;
ll r = 1000000000000000000ll;
while (l < r)
{
ll c = (l + r) / 2ll;
ll s = solve(c);
if (s == K) l = r = c;
if (s > K) l = c;
if (s < K) r = c;
}
solve(l);
cout << res + K * l << '\n';
return 0;
}
