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]:
        if (a - d) not in ameba:
            ameba.append(a - d)
        if (a) not in ameba:
            ameba.append(a)
        if (a + d) not in ameba:
            ameba.append(a + d)

    amebas.append(ameba)

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