// Author: wlzhouzhuan
#include<bits/stdc++.h>
using namespace std;

#define rep(i,l,r) for(int i=(l);i<=(r);i++)
#define per(i,l,r) for(int i=(l);i>=(r);i--)
#define ll long long
#define ull unsigned long long
#define pii pair<int,int>
#define mset(s,t) memset(s,t,sizeof(s))
#define mcpy(s,t) memcpy(s,t,sizeof(t))
#define SZ(x) ((int)x.size())
#define pb push_back
#define eb emplace_back
#define fir first
#define sec second

template<class T1,class T2>bool ckmax(T1 &a,T2 b){if(a<b)return a=b,1;else return 0;}
template<class T1,class T2>bool ckmin(T1 &a,T2 b){if(a>b)return a=b,1;else return 0;}

inline int read(){
    int x=0,f=0;char ch=getchar();
    while(!isdigit(ch))f|=ch=='-',ch=getchar();
    while(isdigit(ch))x=10*x+ch-'0',ch=getchar();
    return f?-x:x;
}
template<typename T>void print(T x){
    if(x<0)putchar('-'),x=-x;
    if(x>=10)print(x/10);
    putchar(x%10+'0');
}
template<typename T>void print(T x,char ch){
    print(x),putchar(ch);
}

const int N=1000005;
const int inf=2e9;

struct Info{
    ll l,r,V;
    Info(ll _x=0,ll _r=0){
        l=_x-_r,r=_x+_r,V=_r*_r;
    }
    friend bool operator < (const Info &a,const Info &b){
        return a.r!=b.r?a.r<b.r:a.l<b.l;
    }
}b[N];

int len;
int a[N],d[N],n;
ll dp[N];

int main(){
    n=read();
    rep(i,1,n)a[i]=read(),d[i]=a[i]-a[i-1];
    d[1]=d[n+1]=inf;
    rep(i,1,n)b[++len]=Info(a[i],min(d[i],d[i+1]));
    rep(i,1,n){
        int nowr=d[i+1];
        per(j,i-1,2){
            int r=d[j+1]-nowr;
            if(r<0||r>d[j]||r>=nowr)break;
            b[++len]=Info(a[j],r);
            nowr=r;
        }
    }
    rep(i,1,n){
        int nowr=d[i];
        rep(j,i+1,n-1){
            int r=d[j]-nowr;
            if(r<0||r>d[j]||r>=nowr)break;
            b[++len]=Info(a[j],r);
            nowr=r;
        }
    }
    sort(b+1,b+len+1);
    rep(i,1,len){
        dp[i]=dp[i-1];
        int j=upper_bound(b+1,b+len+1,Info(b[i].l))-b-1;
        ckmax(dp[i],dp[j]+b[i].V);
    }
    print(dp[len],'\n');
    return 0;
}