Contest Duration: - (local time) (100 minutes) Back to Home
E - Meaningful Mean /

Time Limit: 2 sec / Memory Limit: 256 MB

### 問題文

a の空でない連続する部分列 {a_l, a_{l+1}, …, a_r} (1 ≤ l ≤ r ≤ N)N(N+1)/2 個存在します。これらのうち、算術平均が K 以上であるものは何個あるでしょうか？

### 制約

• 入力値はすべて整数である。
• 1 ≤ N ≤ 2 \times 10^5
• 1 ≤ K ≤ 10^9
• 1 ≤ a_i ≤ 10^9

N K
a_1
a_2
:
a_N

### 出力

a の空でない連続する部分列のうち、算術平均が K 以上であるものの個数を出力せよ。

3 6
7
5
7

### 出力例 1

5

• {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}

これらの平均はそれぞれ 7, 6, 19/3, 5, 6, 7 であり、このうち 6 以上であるものは 5 個です。なお、{a_1} と {a_3} は含まれる要素の値では区別できませんが、これらは個別に数えます。

1 2
1

0

7 26
10
20
30
40
30
20
10

### 出力例 3

13

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.

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.

1 2
1

0

7 26
10
20
30
40
30
20
10

13