num,time = list(map(int, input().split()))

t = input().split()

ans = time

for i in range(0,num-1):

	if int(t[i+1])-int(t[i]) < time:

		ans += int(t[i+1])-int(t[i])

	else:

		ans += time

print(ans)
num,time = list(map(int, input().split()))

t = input().split()

ans = time

for i in range(0,num-1):

 	a = int(t[i+1])-int(t[i]) 

	if a < time:

		ans += a

	else:

		ans += time

print(ans)
num, time = list(map(int, input().split()))
t = input().split()
ans = time
for i in range(0, num - 1):
    if int(t[i + 1]) - int(t[i]) < time:
        ans += int(t[i + 1]) - int(t[i])
    else:
        ans += time
print(ans)

num, time = list(map(int, input().split()))
t = input().split()
ans = time
for i in range(0, num - 1):
    a = int(t[i + 1]) - int(t[i])
    if a < time:
        ans += a
    else:
        ans += time
print(ans)

-    if int(t[i + 1]) - int(t[i]) < time: -        ans += int(t[i + 1]) - int(t[i]) +    a = int(t[i + 1]) - int(t[i]) +    if a < time: +        ans += a