For a finite set of integers X, let f(X)=\max X - \min X.

Given are N integers A_1,...,A_N.

We will choose K of them and let S be the set of the integers chosen. If we distinguish elements with different indices even when their values are the same, there are {}_N C_K ways to make this choice. Find the sum of f(S) over all those ways.

Since the answer can be enormous, print it \bmod (10^9+7).

Constraints

* 1 \leq N \leq 10^5
* 1 \leq K \leq N
* |A_i| \leq 10^9

Input

Input is given from Standard Input in the following format:


N K
A_1 ... A_N


Output

Print the answer \bmod (10^9+7).

Examples

Input

4 2
1 1 3 4


Output

11


Input

6 3
10 10 10 -10 -10 -10


Output

360


Input

3 1
1 1 1


Output

0


Input

10 6
1000000000 1000000000 1000000000 1000000000 1000000000 0 0 0 0 0


Output

999998537
MAX = 110000
MOD = 1000000007
fac = [0]*MAX
finv = [0]*MAX
inv = [0]*MAX
fac[0] = 1
fac[1] = 1
finv[0] = 1
finv[1] = 1
inv[1] = 1
for i in range(2, MAX):
  fac[i] = fac[i-1]*i%MOD
  inv[i] = MOD - inv[MOD%i]*(MOD//i)%MOD
  finv[i] = finv[i-1]*inv[i]%MOD
def COM(n, k):
  if n < 0 or k < 0 or n < k:
    return 0
  return fac[n]*(finv[k]*finv[n-k]%MOD)%MOD

N, K = map(int, input().split())
As = list(map(int, input().split()))
As.sort()
r = 0
for i in reversed(range(N)):
  r = (r+As[i]*COM(i, K-1))%1000000007
  r = (r-As[i]*COM(N-i-1, K-1))%1000000007
  #print(r)
print(r)
