2545: Bear and Bowling
Description
Limak is an old brown bear. He often goes bowling with his friends. Today he feels really good and tries to beat his own record!
For rolling a ball one gets a score − an integer (maybe negative) number of points. Score for i-th roll is multiplied by i and scores are summed up. So, for k rolls with scores s1,s2,...,sk, total score is 
. Total score is 0 if there were no rolls.
Limak made n rolls and got score ai for i-th of them. He wants to maximize his total score and he came up with an interesting idea. He will cancel some rolls, saying that something distracted him or there was a strong wind.
Limak is able to cancel any number of rolls, maybe even all or none of them. Total score is calculated as if there were only non-canceled rolls. Look at the sample tests for clarification. What maximum total score can Limak get?
The first line contains single integer n (1≤n≤105).
The second line contains n space-separated integers a1,a2,...,an (|ai|≤107) - scores for Limak's rolls.
Print the maximum possible total score after choosing rolls to cancel.
5
-2 -8 0 5 -3
13
6
-10 20 -30 40 -50 60
400
In first sample Limak should cancel rolls with scores -8 and -3. Then he is left with three rolls with scores -2,0,5. Total score is 1·(-2)+2·0+3·5=13.
In second sample Limak should cancel roll with score -50. Total score is 1·(-10)+2·20+3·(-30)+4·40+5·60=400.