n, d = list(map(int, input().split()))
A = list(map(int, input().split()))
from collections import defaultdict
D = defaultdict(int)
E = defaultdict(int)
ans = 0
for i in range(n):
    a = A[i]
    D[a] += 1
    E[a] += D[a-d]
    ans += E[a-d]
print(ans)