Codeforces 251A. Points on line (math lower_bound)

Title Link: Http://codeforces.com/problemset/problem/251/A

Little Petya likes points a lot. Recently his mom had presented him N points lying on the line OX. Now Petya are wondering in what many ways he can choose three distinct points so that the distance between the farthest Of them doesn ' t exceed D.

Note that the order of the points inside the group of three chosen points doesn ' t matter.

Input

The first line contains and integers:NandD(1?≤? n. ≤?105; 1?≤? d. ≤?109 ). The next line containsNIntegers x1,? x 2,?...,? x N , their absolute value doesn ' t exceedTen9 -thex-coordinates of the points that Petya have got.

It is guaranteed, the coordinates of the points in the input strictly increase.

Output

Print a single integer-the number of groups of three points, where the distance between both farthest points doesn ' t exce Ed D.

%lld specifier to read or write 64-bit integers inс++. It is preferred to use the cin, cout streams or the %i64dspecifier.

Sample Test (s) input

4 31 2) 3 4

Output

4

Input

4 2-3-2-1 0

Output

2

Input

5 191 10 20 30 50

Output

1

Note

In the first sample any group of three points meets our conditions.

In the seconds sample is 2 groups of three points meet our conditions: { -3,-2,-1} and {-2,-1, 0}.

In the third sample is only one group does: {1, ten, +}.

Test instructions

Give N and K, and then give a set of size n, remove 3 numbers from the collection,
The difference between the maximum number and the minimum number is less than K.

The code is as follows:

#include <cstdio> #include <cstring> #include <algorithm> #include <iostream>using namespace STD; #define LL __int64int Main () {    int n;    LL D;    LL a[100047];    while (~SCANF ("%d%i64d", &n,&d))    {for        (int i = 0; i < n; i++)        {            scanf ("%i64d", &a[i]); c12/>}        LL ans = 0;        for (int i = 1; i < n; i++)        {            LL tt = i (Lower_bound (a,a+i,a[i]-d)-a)-1;            ans+=tt* (tt+1)/2;//c n 2        }        printf ("%i64d\n", ans);    return 0;} /*4 31 2 3 44 2-3-2-1 05 191 10 20 30 50*/

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Codeforces 251A. Points on line (math lower_bound)