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: Accepted)

#include<cstdio>
typedef long long ll;
ll s[210000],t[210000];
ll mergesort(int l,int r)
{
	if(l==r) return 0;
	int mid=(l+r)>>1;
	ll ret=mergesort(l,mid)+mergesort(mid+1,r);
	int i=l,j=mid+1,k=l;
	while(i<=mid&&j<=r)
		if(s[i]>s[j]) t[k++]=s[i++];
		else {t[k++]=s[j++];ret+=(mid-i+1);}
	while(i<=mid) t[k++]=s[i++];
	while(j<=r) t[k++]=s[j++];
	for(int i=l;i<=r;i++) s[i]=t[i];
	return ret;
}
int main()
{
	int n,k;
	scanf("%d%d",&n,&k);
	for(int i=1;i<=n;i++)
	{
		ll x;scanf("%lld",&x);
		x-=k;
		s[i]=s[i-1]+x;
	}
	ll ans=mergesort(0,n);
	printf("%lld\n",ans);
	return 0;
}