from collections import*
n,d,*a=[*map(int,open(0).read().split())]
c=[Counter()for _ in range(3)]
for i in a:
  c[2][i]+=c[1][i-d]
  c[1][i]+=c[0][i-d]
  c[0][i]+=1
print(sum(c[2].values()))