According to the regulations of Berland's army, a reconnaissance unit should consist of exactly two soldiers. Since these two soldiers shouldn't differ much, their heights can differ by at most *d* centimeters. Captain Bob has *n* soldiers in his detachment. Their heights are *a*<sub class="lower-index">1</sub>, *a*<sub class="lower-index">2</sub>, ..., *a*<sub class="lower-index">*n*</sub> centimeters. Some soldiers are of the same height. Bob wants to know, how many ways exist to form a reconnaissance unit of two soldiers from his detachment.

Ways (1, 2) and (2, 1) should be regarded as different.
The first line contains two integers *n* and *d* (1 ≤ *n* ≤ 1000, 1 ≤ *d* ≤ 10<sup class="upper-index">9</sup>) — amount of soldiers in Bob's detachment and the maximum allowed height difference respectively. The second line contains *n* space-separated integers — heights of all the soldiers in Bob's detachment. These numbers don't exceed 10<sup class="upper-index">9</sup>.
# import math
# import re
# import random
def solve():
    t=1
    # t = int(input())
    while(t):
        t-=1
        #n = int(input())
        n,d = [int(x) for x in input().split()]
        h = [int(x) for x in input().split()]
        # s = input()
        h.sort()
        count = 0
        for i in range(n):
            for j in range(n):
                if(i!=j and abs(h[i]-h[j]) <=d):
                    count+=1
            
        print(count)
                


solve()
