import sys
N = input().split()
n = int(N[0])
k = int(N[1])
mas = [int(i) for i in input().split()]
mas.sort()

d = 0
i = 0
b = 10**6
y = 0
res = 0

for a in range(n-1):
	d = mas[a + 1] - mas[a]
	i = d - k
	if i < 0:
		i *= -1
	if i < b:
		b = i
		y = a

for a in range(y, 0, -1):
	if mas[a] - mas[a-1] != k:
		res += mas[a] - mas[a-1] - k
		mas[a-1] = mas[a] - k

for a in range(y, n-1):
	if mas[a + 1] - mas[a] != k:
		res += mas[a+1] - mas[a] - k
		mas[a+1] = mas[a] + k
print(res) 	 
		
def main():
	return 0;
main()