Consider a permutation a1, a2,
, an (all
ai are different integers in range from 1 to n). Let us call k-inversion
a sequence of numbers i1, i2,
, ik such that
1 ≤ i1 < i2 <
< ik ≤ n
and ai1 > ai2 >
> aik. Your task is to evaluate
the number of different k-inversions in a given permutation.
Input
The first line contains integers n and k
(1 ≤ n ≤ 20000; 2 ≤ k ≤ 10).
The second line is filled with n integers ai.
Output
Output the number of different k-inversions in a given permutation. This number must be taken modulo 109.
Samples
input | output |
---|
3 2
3 1 2
| 2 |
5 3
5 4 3 2 1
| 10
|
Problem Author: Dmitry Gozman
Problem Source: Dmitry Gozman Contest 1, Petrozavodsk training camp, January 2007