Problem:
Score : 300 points

Problem Statement

We have a sequence of N integers A~=~A_0,~A_1,~...,~A_{N - 1}.

Let B be a sequence of K \times N integers obtained by concatenating K copies of A. For example, if A~=~1,~3,~2 and K~=~2, B~=~1,~3,~2,~1,~3,~2.

Find the inversion number of B, modulo 10^9 + 7.

Here the inversion number of B is defined as the number of ordered pairs of integers (i,~j)~(0 \leq i < j \leq K \times N - 1) such that B_i > B_j.

Constraints

All values in input are integers.

1 \leq N \leq 2000

1 \leq K \leq 10^9

1 \leq A_i \leq 2000

Input

Input is given from Standard Input in the following format:

N K
A_0 A_1 ... A_{N - 1}

Output

Print the inversion number of B, modulo 10^9 + 7.

Sample Input 1

2 2
2 1

Sample Output 1

3

In this case, B~=~2,~1,~2,~1. We have:

B_0 > B_1

B_0 > B_3

B_2 > B_3

Thus, the inversion number of B is 3.

Sample Input 2

3 5
1 1 1

Sample Output 2

0

A may contain multiple occurrences of the same number.

Sample Input 3

10 998244353
10 9 8 7 5 6 3 4 2 1

Sample Output 3

185297239

Be sure to print the output modulo 10^9 + 7.

Solution in Python (3.4.3) (judge verdict: Accepted)

# -*- coding: utf-8 -*-
N, K = map(int, input().split())
A_list = list(map(int, input().split()))

def count_inversion(target_list):
    return sum(sum(m<n for m in target_list[i+1:]) for i,n in enumerate(target_list))

A_list_copy = A_list
invension_increase = 0
for i in set(A_list):
    max_num = max(A_list_copy)
    max_count = A_list_copy.count(max(A_list_copy))
    A_list_copy = [num for num in A_list_copy if num != max_num]
    invension_increase += max_count * len(A_list_copy)

ans_count = count_inversion(A_list) * K
ans_count += invension_increase * K * (K - 1) // 2

print(ans_count % (10 ** 9 + 7))