#include<bits/stdc++.h>
#define lp(i,j,n) for(int i=j;i<n;i++)
using namespace std;

typedef long long ll;

const int n_=5001;
ll dp[n_][n_];
ll sum[n_][n_];
ll a[n_];
int n;

ll so2(int i,int j){
    ll &ret=sum[i][j];
    if(ret!=-1)return ret;
    if(i==j)return a[i];
    return ret=a[i]+so2(i+1,j);
}
ll so(int i, int j){
    ll &ret= dp[i][j];
    if(ret!=-1)return ret;
    if(i==j)return 0;
    return ret=a[i]*so2(i+1,j)+so(i+1,j);
}
int main() {
    ios_base::sync_with_stdio(0);cin.tie(NULL);
    memset(dp,-1,sizeof dp);
    memset(sum,-1,sizeof sum);
    cin>>n;
    lp(i,0,n)cin>>a[i];
    ll res=0;
    lp(i,0,n)lp(j,i,n)res=max(res,so(i,j));
    cout<<res<<"\n";
}