[Usaco2011 Feb]Generic Cow Protests

时间限制:10s      空间限制:128MB

题目描述


Farmer John's N (1 <= N <= 100,000) cows are lined up in a row and
numbered 1..N. The cows are conducting another one of their strange
protests, so each cow i is holding up a sign with an integer A_i
(-10,000 <= A_i <= 10,000).

FJ knows the mob of cows will behave if they are properly grouped
and thus would like to arrange the cows into one or more contiguous
groups so that every cow is in exactly one group and that every
group has a nonnegative sum.

Help him count the number of ways he can do this, modulo 1,000,000,009.

By way of example, if N = 4 and the cows' signs are 2, 3, -3, and
1, then the following are the only four valid ways of arranging the
cows:

(2 3 -3 1)
(2 3 -3) (1)
(2) (3 -3 1)
(2) (3 -3) (1)

Note that this example demonstrates the rule for counting different
orders of the arrangements.

给出n个数,问有几种划分方案(不能改变数的位置),使得每组中数的和大于等于0。输出方案数除以 1000000009的余数。


输入格式

* Line 1: A single integer: N

* Lines 2..N + 1: Line i + 1 contains a single integer: A_i


输出格式


* Line 1: A single integer, the number of arrangements modulo
        1,000,000,009.


样例输入

4
2
3
-3
1



样例输出

4

提示

没有写明提示


题目来源

Gold