#include <bits/stdc++.h>
using namespace std;
 
int main() {
	// your code goes here
	int n;
	cin>>n;
	int tot=0;
	vector<int> vec(n);
	for(int i=0;i<n;++i){
		cin>>vec[i];
		tot+=vec[i];
		vec[i]=-vec[i];
	}
	vector<int> pre(n,0),suff(n),maxSuff(n);
	for(int i=1;i<=n-3;++i){
		pre[i]=max(vec[i],pre[i-1]+vec[i]);
	}
	suff[n-1]=vec[n-1];
	maxSuff[n-1]=vec[n-1];
	for(int i=n-2;i>=0;--i){
		suff[i]=suff[i+1]+vec[i];
		maxSuff[i]=max(maxSuff[i+1],suff[i]);
	}
	int maxS2S4=INT_MIN;
	for(int i=1;i<=n-3;++i){
		maxS2S4=max(maxS2S4,pre[i]+maxSuff[i+2]);
	}
	int ans = tot+(2*maxS2S4);
	cout<<ans<<endl;
	return 0;
}

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Ngo1IC0yIDMgLTEwMCA0IDU=

6
5 -2 3 -100 4 5