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?≤?109) — 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?109.

Output

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

相似的問題：