inp = input() N, K = map(int, (inp.split())) K = abs(K) inp = input() positions = list(map(int, inp.split())) positions.sort() steps = 0 mid = int(N / 2) for i in range(1, N): if mid - i >= 0: steps += abs(positions[mid] - positions[mid - i]) - K * i if mid + i < N: steps += abs(positions[mid + i] - positions[mid]) - K * i print(abs(steps))