#include <iostream>
#include <iomanip>
#include <vector>
#include <cmath>
#include <algorithm>
#include <set>
#include <queue>
#include <map>
#include <stack>
#include <bitset>
#include <string>
#include <cstring>
#include <iterator>
#include <random>
#define ll long long
#define ld long double
#define inf (ll)(2*1e18)
#define sort(a) sort(a.begin(), a.end())
#define reverse(a) reverse(a.begin(), a.end())
#define pb push_back
#define endl "\n"
using namespace std;
void solve(){
ll n, k, i, x=0, y, res=0;
cin>>n>>k;
vector<ll> a;
for(i=0;i<n;++i){
cin>>y;
if(abs(x + y) == abs(x) + abs(y)){
x += y;
}else{
a.pb(x);
x = y;
}
}
if(x > 0){
a.pb(x);
}
if(!a.empty() and a.front() < 0){
reverse(a);
a.pop_back();
reverse(a);
}
set<pair<ll, ll>> s1, s2;
for(i=0;i<a.size();++i){
s1.insert({abs(a[i]), i});
s2.insert({i, a[i]});
}
while((s2.size() + 1)/2 > k){
x = s1.begin()->second;
s1.erase(s1.begin());
auto it = s2.lower_bound({x, -inf});
if(it == s2.begin()){
s2.erase(s2.begin());
s1.erase({abs(s2.begin()->second), s2.begin()->first});
s2.erase(s2.begin());
}else if(it == --s2.end()){
s2.erase(it);
it = --s2.end();
s1.erase({abs(it->second), it->first});
s2.erase(it);
}else{
y = it->second;
--it;
y += it->second;
++it;
++it;
y += it->second;
s1.erase({abs(it->second), it->first});
s2.erase(it);
it = s2.lower_bound({x, -inf});
--it;
s1.erase({abs(it->second), it->first});
s2.erase(it);
it = s2.lower_bound({x, -inf});
s2.erase(it);
s1.insert({abs(y), x});
s2.insert({x, y});
}
}
for(auto it=s2.begin();it!=s2.end();++it){
if(it->second > 0){
res += it->second;
}
}
cout<<res<<endl;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
srand(time(nullptr));
ll t=1;
// cin>>t;
for(;t>0;--t){
solve();
}
return 0;
}
