n, d, t = map(int, input().split())
amebas = []
amebas.append(list(map(int, input().split())))

for i in range(t):
    ameba = []
    for a in amebas[i]:
        ameba.append(a - 3)
        ameba.append(a)
        ameba.append(a + 3)

    amebas.append(ameba)

print(len(set(amebas[-1])))