## https://yukicoder.me/problems/no/3456

from collections import deque

def main():
    N, D = map(int, input().split())
    A = list(map(int, input().split()))

    d_map = {}
    for a in A:
        b = a % D
        if b not in d_map:
            d_map[b] = []
        d_map[b].append((a - b) // D)
    
    answer = 0
    for array in d_map.values():
        dp_map = {}
        for a in array:
            if a not in dp_map:
                dp_map[a] = [0, 0]

            if (a - 1) in dp_map:
                answer += dp_map[a - 1][1]
                dp_map[a][1] += dp_map[a - 1][0]
                
            dp_map[a][0] += 1

    print(answer)





                




if __name__ == "__main__":
    main()