#include <bits/stdc++.h>
using namespace std;
long long n,k,x,ans=0,cnt=0,f=1,lnei[600001]={0},rnei[600001]={0},l[600001]={0},r[600001]={0},vld[600001]={0},sum[600001]={0};
vector<long long> a,val;
priority_queue<pair<long long,int> > q;
void solve()
{
a.push_back(0);
val.push_back(0);
cin>>n>>k;
for(int i=1;i<=n;i+=1)
{
cin>>x;
if(x!=0) a.push_back(x);
}
n=a.size()-1;
k=min(k,n);
int ind=1;
while(ind<a.size() && a[ind]<0) ind+=1;
if(ind==a.size())
{
cout<<0;
return;
}
long long pre=0;
for(int i=ind;i<=n;i+=1)
{
if(f*a[i]>0) pre+=a[i];
else
{
if(pre>0)
{
ans+=pre;
cnt+=1;
}
val.push_back(pre);
pre=a[i];
f=-f;
}
}
if(pre>0)
{
ans+=pre;
cnt+=1;
}
val.push_back(pre);
//for(int i=1;i<val.size();i+=1) cout<<val[i]<<" ";
if(cnt<=k)
{
cout<<ans;
return;
}
int tot=val.size()-1;
for(int i=1;i<=tot;i+=1) sum[i]=val[i]+sum[i-1];
for(int i=1;i<=tot;i+=1)
{
l[i]=r[i]=i;
lnei[i]=i-1;
rnei[i]=(i+1)%(tot+1);
vld[i]=1;
q.push(make_pair(-abs(a[i]),i));
}
while(cnt>k)
{
long long d=q.top().first;
int id=q.top().second;
q.pop();
if(vld[id]==0) continue;
ans+=d;
vld[id]=0;
if(vld[l[id]]==1 && vld[r[id]]==1) cnt-=1;
tot+=1;
vld[tot]=1;
lnei[tot]=lnei[lnei[id]];
rnei[tot]=rnei[rnei[id]];
l[tot]=vld[lnei[tot]]==1 ? l[lnei[tot]] : lnei[id];
l[tot]=vld[rnei[tot]]==1 ? r[lnei[tot]] : rnei[id];
if(vld[lnei[tot]]) rnei[lnei[tot]]=tot;
if(vld[rnei[tot]]) lnei[rnei[tot]]=tot;
vld[rnei[id]]=vld[lnei[id]]=0;
if(val[l[tot]]<0) q.push(make_pair(sum[r[tot]]-sum[l[tot]-1],tot));
else q.push(make_pair(-sum[r[tot]]+sum[l[tot]-1],tot));
cnt-=1;
}
cout<<ans;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int t=1;
//cin>>t;
while(t--) solve();
return 0;
}
