BALLLSTA - Ball Stack

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The XYZ TV channel is developing a new game show, where a contestant has to make some choices in order to get a prize. The game consists of a triangular stack of balls, each of them having an integer value, as the following example shows.

 

\epsfbox{p12357.eps}

The contestant must choose which balls he is going to take and his prize is the sum of the values of those balls. However, the contestant can take any given ball only if he also takes the balls directly on top of it. This may require taking additional balls using the same rule. Notice that the contestant may choose not to take any ball, in which case the prize is zero.

The TV show director is concerned about the maximum prize a contestant can make for a given stack. Since he is your boss and he does not know how to answer this question, he assigned this task to you.

 

Input:

Each test case is described using several lines. The first line contains an integer N representing the number of rows of the stack ( 1$ \le$N$ \le$1000). The i-th of the next N lines contains i integers Bij ( -105$ \le$Bij$ \le$105 for 1$ \le$j$ \le$i$ \le$N); the number Bij is the value of the j-th ball in the i-th row of the stack (the first row is the topmost one, and within each row the first ball if the leftmost one).

The last test case is followed by a line containing one zero.

 

Output:

For each test case output a line with an integer representing the maximum prize a contestant can make from the stack.

Sample input:

4
3
-5 3
-8 2 -8
3 9 -2 7
2
-2
1 -10
3
1
-5 3
6 -4 1
0

 

Sample output:

7
0
6

hide comments
(Tjandra Satria Gunawan)(曾毅昆): 2013-05-18 11:07:57

picture is broken because this site: https://icpcarchive.ecs.baylor.edu/ is now unavailable. please fix this..

Ashish Lavania: 2012-12-22 12:53:41

Last edit: 2013-12-10 15:59:46
:D: 2012-08-05 20:21:23

Remember that you can pick any number of balls, that is apart from the "on top" rule balls.

Jared Deckard: 2012-07-30 23:28:28

balls


Added by:Gareev
Date:2012-07-30
Time limit:1.071s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ASM64
Resource:ACM Latin America 2011