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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
struct BiIndTree{
	long long val[200005];
	void init(){
		memset(val,0,sizeof(val));
	}
	void add(int x,long long v){
		x++;
		while(x<200000){
			val[x]+=v;
			x+=x&-x;
		} 
	}
	long long query(int x){
		x++;
		long long res=0;
		while(x>0){
			res+=val[x];
			x-=x&-x;
		}
		return res;
	}
}bit; 
int n;
long long k;
long long sum[200005];
long long ans;
vector<long long> s;
int main(){
	cin>>n>>k;
	int sz=0;
	sum[sz++]=0;
	for(int i=0;i<n;++i){
		cin>>sum[sz];
		sum[sz]-=k;
		sum[sz]+=sum[sz-1];
		sz++;
	}
	for(int i=0;i<sz;++i){
		s.push_back(sum[i]);
	}
	sort(s.begin(),s.end());
	s.erase(unique(s.begin(),s.end()),s.end());
	bit.init();
	for(int i=0;i<sz;++i){
		int pos=lower_bound(s.begin(),s.end(),sum[i])-s.begin();
		ans+=bit.query(pos);
		bit.add(pos,1);
	} 
	cout<<ans<<'\n';
	return 0;
}