n = 5
lost = [2, 4]
reserve = [1, 3, 5]

lost.sort()
reserve.sort()

new_lost = []
new_reserve = []

for l in lost:
    if l not in reserve:
        new_lost.append(l)

for r in reserve:
    if r not in lost:
        new_reserve.append(r)

lost = new_lost
reserve = new_reserve

for r in reserve:
    if r - 1 in lost:
        lost.remove(r - 1)
    elif r + 1 in lost:
        lost.remove(r + 1)

answer = n - len(lost)
print(answer)