Problems
K-inversions
K-inversions
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 two integers n and k (1 ≤ n ≤ 20000, 2 ≤ k ≤ 10). The second line is filled with n numbers ai
.
Output
Output a single number — the number of k-inversions in a given permutation. The number must be taken modulo 109
.
Input example #1
3 2 3 1 2
Output example #1
2