Petya and Array

题意翻译

有一个长度为 $n$ 的序列 $a$，和一个数 $t$，求有多少个区间 $[l,r]$ 满足 $a_l+a_{l+1}+...+a_{r} <t $ 且 $l\le r$。

题目描述

Petya has an array $ a $ consisting of $ n $ integers. He has learned partial sums recently, and now he can calculate the sum of elements on any segment of the array really fast. The segment is a non-empty sequence of elements standing one next to another in the array. Now he wonders what is the number of segments in his array with the sum less than $ t $ . Help Petya to calculate this number. More formally, you are required to calculate the number of pairs $ l, r $ ( $ l \le r $ ) such that $ a_l + a_{l+1} + \dots + a_{r-1} + a_r < t $ .

输入输出格式

输入格式

The first line contains two integers $ n $ and $ t $ ( $ 1 \le n \le 200\,000, |t| \le 2\cdot10^{14} $ ). The second line contains a sequence of integers $ a_1, a_2, \dots, a_n $ ( $ |a_{i}| \le 10^{9} $ ) — the description of Petya's array. Note that there might be negative, zero and positive elements.

输出格式

Print the number of segments in Petya's array with the sum of elements less than $ t $ .

输入输出样例

输入样例 #1

5 4
5 -1 3 4 -1

输出样例 #1

5

输入样例 #2

3 0
-1 2 -3

输出样例 #2

4

输入样例 #3

4 -1
-2 1 -2 3

输出样例 #3

3

说明

In the first example the following segments have sum less than $ 4 $ : - $ [2, 2] $ , sum of elements is $ -1 $ - $ [2, 3] $ , sum of elements is $ 2 $ - $ [3, 3] $ , sum of elements is $ 3 $ - $ [4, 5] $ , sum of elements is $ 3 $ - $ [5, 5] $ , sum of elements is $ -1 $