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 $a_l + a_{l+1} + \dots + a_{r-1} + a_r < t$.
Input
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.
Output
Print the number of segments in Petya's array with the sum of elements less than $t$.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
样例输出
提示
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 $-1$