N,T = [int(i) for i in input().split()]

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

ret = 0

ind = 1

while ind < len(ts):

    ret += min(T,ts[ind]-ts[ind-1])

    ind += 1

print((ret+T))

N,T = [int(i) for i in input().split()]

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

ret = 0

for ind in range (1, N):

    ret += min(T,ts[ind]-ts[ind-1])

print((ret+T))

N, T = [int(i) for i in input().split()]
ts = [int(i) for i in input().split()]
ret = 0
ind = 1
while ind < len(ts):
    ret += min(T, ts[ind] - ts[ind - 1])
    ind += 1
print((ret + T))

N, T = [int(i) for i in input().split()]
ts = [int(i) for i in input().split()]
ret = 0
for ind in range(1, N):
    ret += min(T, ts[ind] - ts[ind - 1])
print((ret + T))

-ind = 1 -while ind < len(ts): +for ind in range(1, N): -    ind += 1