Problem:
Score : 400 points

Problem Statement

Takahashi has N sticks that are distinguishable from each other. The length of the i-th stick is L_i.

He is going to form a triangle using three of these sticks. Let a, b, and c be the lengths of the three sticks used. Here, all of the following conditions must be satisfied:

a < b + c

b < c + a

c < a + b

How many different triangles can be formed? Two triangles are considered different when there is a stick used in only one of them.

Constraints

All values in input are integers.

3 \leq N \leq 2 \times 10^3

1 \leq L_i \leq 10^3

Input

Input is given from Standard Input in the following format:

N
L_1 L_2 ... L_N

Constraints

Print the number of different triangles that can be formed.

Sample Input 1

4
3 4 2 1

Sample Output 1

1

Only one triangle can be formed: the triangle formed by the first, second, and third sticks.

Sample Input 2

3
1 1000 1

Sample Output 2

0

No triangles can be formed.

Sample Input 3

7
218 786 704 233 645 728 389

Sample Output 3

23

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)


import java.util.*;

class Main {



	public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Integer L[] = new Integer[N];
        int count = 0;
        int check = 0;
        int a = 0;
        int b = 0;
        int c = 0;

        for(int i=0; i<N; i++){
            L[i] = sc.nextInt();
        }

        Arrays.sort(L, Comparator.reverseOrder());

        for(int i=0; i < N-2; i++){
            check = 0;
            for(int j=i+1; check ==0 && j < N-1; j++){
                for(int k=j+1; check ==0 && k < N; k++){
                    a = L[i];
                    b = L[j];
                    c = L[k];

                    if(a < b+c){
                        count++;
                    } else {
                        check = 1;
                    }
                }
            }
        }


        System.out.println(count);

    }



}