N, D, T = map(int, input().split())
ameba = {}
x = list(map(int, input().split()))

for i in x:
    ameba[i] = 1

for i in range(T):
    ameba_x = ameba.copy()
    for k, v in ameba_x.items():
        k1 = k - D
        k2 = k + D
        ameba[k1] = 1
        ameba[k2] = 1

print(len(ameba))