#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define ll long long 
#define mod 1000000007
using namespace std;
inline int read()
{int x=0,f=0;
char c=getchar();
while (c<'0'||c>'9') 
{if (c=='-') f=1;
c=getchar();
}
while (c>='0'&&c<='9') x=x*10+c-'0',c=getchar();
if (f) x=-x;
return x;
}
int a[500005],n;
ll s1[500005];
ll s2[500005];
ll ans=0;
inline ll calc(int d)
{ll maxn=0;
for (int i=1;i+d-1<=n;i++)
{ll res=(s1[i+d-1]-s1[i-1])*(s1[i+d-1]-s1[i-1]);
res-=(s2[i+d-1]-s2[i-1]);
if (res>maxn) maxn=res;
}
return maxn;
}
int main (){
	int i,j,k;
	n=read();
	for (i=1;i<=n;i++)
	{a[i]=read();}
	for (i=1;i<=n;i++)
	{s1[i]=s1[i-1]+a[i];
	s2[i]=s2[i-1]+a[i]*a[i];
	}
	srand((unsigned long long)new char);
	while (((double)(clock()))/CLOCKS_PER_SEC<1.95)
	{int l=1,r=n;
	while (l+5<=r)
	{int m1=l+rand()%(r-l+1);
	int m2=r-rand()%(r-l+1);
	if (m1>m2) swap(m1,m2);
	ll t1=calc(m1),t2=calc(m2);
	if (t1>ans) ans=t1;
	if (t2>ans) ans=t2;
	if (t1>t2) {r=m2;}
	else {l=m1;}
	}
	for (int i=max(0,l-10);i<=min(n,l+10);i++)
	{ans=max(ans,calc(i));}
	}
	printf ("%lld\n",ans/2);
	return 0;
}