Petya and Array
时间限制:C/C++/Rust/Pascal 2秒,其他语言4秒
空间限制:C/C++/Rust/Pascal 256 M,其他语言512 M
64bit IO Format: %lld

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 $$$a_l + a_{l+1} + \dots + a_{r-1} + a_r < t$$$.

输入描述:

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.

输出描述:

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

示例1

输入

复制
5 4
5 -1 3 4 -1

输出

复制
5
示例2

输入

复制
3 0
-1 2 -3

输出

复制
4
示例3

输入

复制
4 -1
-2 1 -2 3

输出

复制
3

备注:

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 $$$-1$$$