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 (3.8.2) (judge verdict: Accepted)

n, k = map(int, input().split())
A = [int(input()) for i in range(n)]
A = [a-k for a in A]

from itertools import accumulate
C = [0]+A
C = list(accumulate(C))
#print(C)

class BIT:
    def __init__(self, n):
        self.n = n
        self.bit = [0]*(self.n+1) # 1-indexed

    def init(self, init_val):
        for i, v in enumerate(init_val):
            self.add(i, v)

    def add(self, i, x):
        i += 1 # to 1-indexed
        while i <= self.n:
            self.bit[i] += x
            i += (i & -i)

    def sum(self, i, j):
        # return sum of [i, j)
        return self._sum(j) - self._sum(i)

    def _sum(self, i):
        # return sum of [0, i)
        res = 0
        while i > 0:
            res += self.bit[i]
            i -= i & (-i)
        return res

B = list(set(C))
B.sort(reverse=True)
D = {}
for i, b in enumerate(B):
    D[b] = i

C = [D[c] for c in C]
bit = BIT(max(C)+1)
ans = 0
for c in C:
    ans += bit.sum(c, bit.n)
    bit.add(c, 1)
print(ans)