Beautiful Triplets

Count beautiful triplets: three indices i < j < k where arr[j] - arr[i] = d and arr[k] - arr[j] = d. The array is strictly increasing. Example: arr=[1,2,4,5,7,8,10], d=3 → Triplets: (1,4,7) with values (1,4,7), (2,5,8) with values (2,5,8), (4,7,10) with values (4,7,10) → Answer: 3

Entrada

First line: n d (space-separated). Second line: n space-separated integers (the array).

Salida

A single integer: the count of beautiful triplets.

Ejemplo

7 3
1 2 4 5 7 8 10

Esperado

3