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

t = list(map(int,input().split()))

a = T



for i in range(N-1):

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



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

t = list(map(int,input().split()))

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

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

-a = T -for i in range(N - 1): -    a += min(T, t[i + 1] - t[i]) -print(a) +print((T + sum([min(T, t[i + 1] - t[i]) for i in range(N - 1)])))