N,T=list(map(int,input().split()))

t=[int(i) for i in input().split()]

ans = T

for i in range(N-1):

    ans += min(t[i+1] - t[i],T)

print(ans)
N,T= list(map(int,input().split()))

t = [int(j) for j in input().split()]

ans =T

b = 0

for i in t:

    ans+=min(i-b,T)

    b = i

print(ans)
N, T = list(map(int, input().split()))
t = [int(i) for i in input().split()]
ans = T
for i in range(N - 1):
    ans += min(t[i + 1] - t[i], T)
print(ans)

N, T = list(map(int, input().split()))
t = [int(j) for j in input().split()]
ans = T
b = 0
for i in t:
    ans += min(i - b, T)
    b = i
print(ans)

-t = [int(i) for i in input().split()] +t = [int(j) for j in input().split()] -for i in range(N - 1): -    ans += min(t[i + 1] - t[i], T) +b = 0 +for i in t: +    ans += min(i - b, T) +    b = i