Problem:
Score : 500 points

Problem Statement

Let N be a positive integer.

There is a numerical sequence of length 3N, a = (a_1, a_2, ..., a_{3N}).
Snuke is constructing a new sequence of length 2N, a', by removing exactly N elements from a without changing the order of the remaining elements.
Here, the score of a' is defined as follows: (the sum of the elements in the first half of a') - (the sum of the elements in the second half of a').

Find the maximum possible score of a'.

Constraints

1 ≤ N ≤ 10^5

a_i is an integer.

1 ≤ a_i ≤ 10^9

Partial Score

In the test set worth 300 points, N ≤ 1000.

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 ... a_{3N}

Output

Print the maximum possible score of a'.

Sample Input 1

2
3 1 4 1 5 9

Sample Output 1

1

When a_2 and a_6 are removed, a' will be (3, 4, 1, 5), which has a score of (3 + 4) - (1 + 5) = 1.

Sample Input 2

1
1 2 3

Sample Output 2

-1

For example, when a_1 are removed, a' will be (2, 3), which has a score of 2 - 3 = -1.

Sample Input 3

3
8 2 2 7 4 6 5 3 8

Sample Output 3

5

For example, when a_2, a_3 and a_9 are removed, a' will be (8, 7, 4, 6, 5, 3), which has a score of (8 + 7 + 4) - (6 + 5 + 3) = 5.

Solution in Python (3.4.3) (judge verdict: Accepted)

import heapq
N = int(input())
A = list(map(int, input().split()))

L = A[:N]
R = [-a for a in A[-N:]]
mid = A[N:-N]

heapq.heapify(L)
heapq.heapify(R)

Lsum = [sum(L)]
Rsum = [sum(R)]

for m in mid:
    if m > L[0]:
        Lsum.append(Lsum[-1] + m - L[0])
        heapq.heappushpop(L, m)
    else:
        Lsum.append(Lsum[-1])

for m in mid[::-1]:
    if -m > R[0]:
        Rsum.append(Rsum[-1] - m - R[0])
        heapq.heappushpop(R, -m)
    else:
        Rsum.append(Rsum[-1])
Rsum = Rsum[::-1]


ans = -10 ** 18
for x, y in zip(Lsum, Rsum):
    ans = max(ans, x + y)

print(ans)