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>.
"""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 a1, a2, ..., an 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.

Input
The first line contains two integers n and d (1 <= n <= 1000, 1 <= d <= 1e9)
    - 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 1e9.

Output
Output one number - amount of ways to form a reconnaissance unit of two soldiers,
    whose height difference doesn't exceed d."""

n, d = map(int, input().split())
sHeight = input().split()
sHeight.sort()

result = 0
for i in range(0, n - 1):
    for j in range(i + 1, n):
        if (int(sHeight[j]) - int(sHeight[i])) <= d:
            result += 2
        else:
            break

print(str(result))