#include<bits/stdc++.h>
#define int long long
#define nl endl
using namespace std;
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(NULL);cout.tie(NULL);
int n, k;
cin>>n>>k;
int a[n];
for(int i=0; i<n; i++) cin>>a[i];
set<pair<int,int> > idx;
set<pair<pair<int,int>, int> > main;
int sum = a[0];
for(int i=1; i<n; i++){
if(a[i] == 0) continue;
if((a[i] >= 0 and a[i-1] >= 0) or (a[i] <= 0 and a[i-1] <= 0)){
sum += a[i];
}else{
idx.insert(make_pair(i, sum));
sum = a[i];
}
}
idx.insert(make_pair(n, sum));
if((*idx.begin()).second < 0) idx.erase(idx.begin());
if(idx.size() > 1 and (*prev(idx.end())).second < 0) idx.erase(prev(idx.end()));
for(auto x : idx){
main.insert(make_pair(make_pair(abs(x.second), (x.second > 0)), x.first));
}
while((main.size()+1)/2 > k){
int x = (*main.begin()).first.first * ((*main.begin()).first.second ? 1 : -1), i = (*main.begin()).second;
auto it = idx.find(make_pair(i, x));
pair<int,int> l = make_pair(0,0), r = make_pair(0,0);
if(it != idx.begin()) l = *prev(it);
if(next(it) != idx.end()) r = *next(it);
main.erase(main.begin());
main.erase(make_pair(make_pair(abs(l.second), (l.second > 0)), l.first));
main.erase(make_pair(make_pair(abs(r.second), (r.second > 0)), r.first));
main.insert(make_pair(make_pair(abs(x + l.second + r.second), (x + l.second + r.second > 0)), i));
if(it != idx.begin()) idx.erase(prev(it));
if(next(it) != idx.end()) idx.erase(next(it));
idx.erase(it);
idx.insert(make_pair(i, x + l.second + r.second));
auto rem = idx.find(make_pair(i, x + l.second + r.second));
if((rem == idx.begin() or next(rem) == idx.end()) and x > 0){
main.erase(make_pair(make_pair(abs(x + l.second + r.second), (x + l.second + r.second > 0)), i));
idx.erase(rem);
}
}
sum = 0;
for(auto x : main){
if(x.first.second) sum += x.first.first;
}
cout<<sum;
return 0;
}
