def pickingNumbers(a):
    cnt = [0] * (max(a) + 1)
    for num in a:
        cnt[num] += 1

    res = 0
    for i in range(len(cnt) - 1):
        curr_sum = cnt[i] + cnt[i + 1]
        if curr_sum > res:
            res = curr_sum
    return res