Treasures

N (1 <= N <= 1,000) treasures have been buried and can be dug out
to earn money. While digging is expensive, finding a treasure can
create tremendous profit (after expenses are subtracted from the
treasure's value). Create a program to compute the maximum profit
possible from a set of buried treasures.

The treasures each have value Pi (1 <= Pi <= 1,000,000) and are
buried on a two-dimensional grid split into squares, each with
coordinates Xi,Yi (-10,000 <= Xi <= 10,000 and -10,000 <= Yi < 0).

Digging the square with coordinates (x, y) is permitted only if y
= -1 or if the three squares with coordinates (x-1, y+1), (x, y+1)
and (x+1, y+1) have already been dug. The cost for digging a square
is 1. When a treasure is dug out, its value is considered earned.

Determine the maximum possible profit by digging the optimal number
of treasures (which might be 0).

PROBLEM NAME: treasures

INPUT FORMAT:

* Line 1: The single integer N

* Lines 2..N+1: Line i+1 contains three space-separated integers: Xi,
        Yi, and Pi.

SAMPLE INPUT:

2
7 -2 9
8 -10 20

OUTPUT FORMAT:

* Line 1: A single integer that is the maximum achievable profit

SAMPLE OUTPUT:

5