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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;
import java.io.PrintWriter;
public class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		int k=sc.nextInt();
		double[] a=new double[n];
		double[] tmp=new double[n];
		long ans=0;
		for(int i=0; i<n; i++){
			a[i]=sc.nextInt()-k;
			if(i!=0){
				a[i]+=a[i-1];
			}
			tmp[i]=a[i];
			if(tmp[i]>=0){
				ans++;
			}
		}
		Arrays.sort(tmp);
		for(int i=0; i<n; i++){
			a[i]=-Arrays.binarySearch(tmp,a[i]+0.1);
		}
		BIT b=new BIT(n+1);
		for(int i=0; i<n; i++){
			ans+=b.get((int)a[i]);
			b.add((int)a[i]);
		}
		System.out.println(ans);
	}
	static class BIT{
		int n;
		int[] data;
		BIT(int n){
			this.n=n;
			data = new int[n+1];
		}
		void add(int i){
			for(;i<=n;i+=i&(-i))data[i]++;
		}
		int get(int i){
			int res = 0;
			for(;i>0;i-=i&(-i))res+=data[i];
			return res;
		}
	}
}