[POI2013] BAJ-Bytecomputer

给定一个长度为 $n$ 的只包含 $-1,0,1$ 的数列 $a$，每次操作可以使 $a_i\gets a_i+a_{i-1}$，求最少操作次数使得序列单调不降。如果不可能通过该操作使得序列单调不降，请输出 `BRAK`。 数据范围：$1\le n\le 10^6$。

A sequence of  integers  from the set  is given. The bytecomputer is a device that allows the following operation on the sequence: incrementing  by  for any . There is no limit on the range of integers the bytecomputer can store, i.e., each  can (in principle) have arbitrarily small or large value. Program the bytecomputer so that it transforms the input sequence into a non-decreasing sequence (i.e., such that ) with the minimum number of operations.

The first line of the standard input holds a single integer  (), the number of elements in the (bytecomputer's) input sequence. The second line contains  integers  () that are the successive elements of the (bytecomputer's) input sequence, separated by single spaces. In tests worth 24% of the total points it holds that , and in tests worth 48% of the total points it holds that .

The first and only line of the standard output should give one integer, the minimum number of operations the bytecomputer has to perform to make its input sequence non-decreasing, of the single word BRAK (Polish for none) if obtaining such a sequence is impossible.

6
-1 1 0 -1 0 1

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