from collections import Counter

N, D = [int(s) for s in input().split()]
A = [int(s) for s in input().split()]

all_cnt = Counter(A)
cnt = Counter()

ans = 0

for a in A:
    ans += cnt[a - D] * (all_cnt[a + D] - cnt[a + D])
    cnt[a] += 1

print(ans)