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 C (GCC 5.4.1) (judge verdict: Runtime Error)

#include<stdio.h>
#include<stdint.h>
#define MOD 1000000007
#define ll long long int
#define rep(i,n) for(i=0;i<n;i++)
ll i,j;

int main(void){
  int n;
  ll k,count;
  uint64_t  p;
  scanf("%d%lld",&n,&k);
  int a[n];
  rep(i,n){scanf("%d",&a[i]);}
  p=k*n;
  int c[p];
  for(j=0;j<k;j++){
    for(i=0+j*n;i<(j+1)*n;i++){c[i]=a[i];}}
  count=0;
  for(j=1;j<p;j++){
    rep(i,j){
      if(c[j]<c[i]){
	count++;
	count%=MOD;
      }
    }
  }
  printf("%lld\n",count);

  return 0;
}