Problem:
Score : 600 points

Problem Statement

You are given an integer sequence of length N, a = {a_1, a_2, …, a_N}, and an integer K.

a has N(N+1)/2 non-empty contiguous subsequences, {a_l, a_{l+1}, …, a_r} (1 ≤ l ≤ r ≤ N). Among them, how many have an arithmetic mean that is greater than or equal to K?

Constraints

All input values are integers.

1 ≤ N ≤ 2 \times 10^5

1 ≤ K ≤ 10^9

1 ≤ a_i ≤ 10^9

Input

Input is given from Standard Input in the following format:

N K
a_1
a_2
:
a_N

Output

Print the number of the non-empty contiguous subsequences with an arithmetic mean that is greater than or equal to K.

Sample Input 1

3 6
7
5
7

Sample Output 1

5

All the non-empty contiguous subsequences of a are listed below:

{a_1} = {7}

{a_1, a_2} = {7, 5}

{a_1, a_2, a_3} = {7, 5, 7}

{a_2} = {5}

{a_2, a_3} = {5, 7}

{a_3} = {7}

Their means are 7, 6, 19/3, 5, 6 and 7, respectively, and five among them are 6 or greater. Note that {a_1} and {a_3} are indistinguishable by the values of their elements, but we count them individually.

Sample Input 2

1 2
1

Sample Output 2

0

Sample Input 3

7 26
10
20
30
40
30
20
10

Sample Output 3

13

Solution in Python (3.4.3) (judge verdict: Runtime Error)

class BinaryIndexedTree:
  def __init__(self, size):
    self.data = [0] * (size+1)
    self.size = size
  
  def add(self, i, w):
    while i <= self.size:
      self.data[i] += w
      i += i & -i

  def sum(self, i):
    result = 0
    while i > 0:
      result += self.data[i]
      i -= i & -i
    return result

from itertools import accumulate,repeat

N,K = map(int, input().split())

B = [0] + [sa-sk for sa,sk in zip(accumulate(int(input())), accumulate(repeat(K, N)))]

lookup = dict(((b,i+1) for i,b in enumerate(sorted(B))))

result = 0
bit = BinaryIndexedTree(N+1)

for b in B:
  c = lookup[b]
  result += bit.sum(c)
  bit.add(c,1)

print(result)