from collections import defaultdict, Counter
N,D = list(map(int,input().split()))
A = list(map(int,input().split()))
left = defaultdict(int)
right = Counter(A)

ans = 0
for i in range(N):
    right[A[i]] -= 1
    
    ans += left[A[i] - D] * right[A[i] + D]

    left[A[i]] += 1
print(ans)