n,t = (int(i) for i in input().split())

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



total = 0



for i in range(1,len(ni)) :

  delta = ni[i] - ni[i-1]

  if delta < t :

    total += delta

  else :

    total += t



    

print((total+t))
def main():

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

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

    s, e = 0, 0

    ans = 0

    for i in range(N):

        if t[i] <= e:

            e = t[i] + T

        else:

            ans += e - s

            s = t[i]

            e = t[i] + T

    ans += e - s

    print(ans)





main()

n, t = (int(i) for i in input().split())
ni = [int(i) for i in input().split()]
total = 0
for i in range(1, len(ni)):
    delta = ni[i] - ni[i - 1]
    if delta < t:
        total += delta
    else:
        total += t
print((total + t))

def main():
    N, T = list(map(int, input().split()))
    t = list(map(int, input().split()))
    s, e = 0, 0
    ans = 0
    for i in range(N):
        if t[i] <= e:
            e = t[i] + T
        else:
            ans += e - s
            s = t[i]
            e = t[i] + T
    ans += e - s
    print(ans)


main()

-n, t = (int(i) for i in input().split()) -ni = [int(i) for i in input().split()] -total = 0 -for i in range(1, len(ni)): -    delta = ni[i] - ni[i - 1] -    if delta < t: -        total += delta -    else: -        total += t -print((total + t)) +def main(): +    N, T = list(map(int, input().split())) +    t = list(map(int, input().split())) +    s, e = 0, 0 +    ans = 0 +    for i in range(N): +        if t[i] <= e: +            e = t[i] + T +        else: +            ans += e - s +            s = t[i] +            e = t[i] + T +    ans += e - s +    print(ans) + + +main()