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 <cstdio>
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
using namespace std;
long long ans=0;
const int N=200010;
int a[N],b[N];
void solve(int l,int r){
    if(l>=r) return;
    int M=l+r>>1,i=l,j=M+1,k=l-1;
    solve(l,M);
    solve(M+1,r);
    while(i<=M&&j<=r){
        if(a[i]<=a[j]) b[++k]=a[i++];
        else b[++k]=a[j++],ans+=i-l;
    }
    while(i<=M) b[++k]=a[i++];
    while(j<=r) b[++k]=a[j++],ans+=i-l;
    for(i=l;i<=r;i++) a[i]=b[i];
}
int main(){
    int n,k,i;
    scanf("%d %d",&n,&k);
    for(i=1;i<=n;i++)
        scanf("%d",&a[i]),a[i]-=k,a[i]+=a[i-1];
    a[0]=0;
    solve(0,n);
    printf("%lld\n",ans);
    return 0;
}