Problem:
Score : 500 points

Problem Statement

On a two-dimensional plane, there are m lines drawn parallel to the x axis, and n lines drawn parallel to the y axis.
Among the lines parallel to the x axis, the i-th from the bottom is represented by y = y_i.
Similarly, among the lines parallel to the y axis, the i-th from the left is represented by x = x_i.

For every rectangle that is formed by these lines, find its area, and print the total area modulo 10^9+7.

That is, for every quadruple (i,j,k,l) satisfying 1\leq i < j\leq n and 1\leq k < l\leq m, find the area of the rectangle formed by the lines x=x_i, x=x_j, y=y_k and y=y_l, and print the sum of these areas modulo 10^9+7.

Constraints

2 \leq n,m \leq 10^5

-10^9 \leq x_1 < ... < x_n \leq 10^9

-10^9 \leq y_1 < ... < y_m \leq 10^9

x_i and y_i are integers.

Input

Input is given from Standard Input in the following format:

n m
x_1 x_2 ... x_n
y_1 y_2 ... y_m

Output

Print the total area of the rectangles, modulo 10^9+7.

Sample Input 1

3 3
1 3 4
1 3 6

Sample Output 1

60

The following figure illustrates this input:

The total area of the nine rectangles A, B, ..., I shown in the following figure, is 60.

Sample Input 2

6 5
-790013317 -192321079 95834122 418379342 586260100 802780784
-253230108 193944314 363756450 712662868 735867677

Sample Output 2

835067060

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Collections;
using System.Text;
using System.Numerics;

class p
{

    static void Main(string[] args)
    {
        //解説みて実装した
        //変数の間違いに気づけず出力違いでだいぶ悩んだ。。。。
        //BItempはBigIntegerのなごり⇒上のバグがBigIntegerの原因かと思ってLongに書き換えた。
        long Xsum = 0;
        long Ysum = 0;
        long BItemp;

        string[] input = Console.ReadLine().Split();
        long N = long.Parse(input[0]);
        long M = long.Parse(input[1]);

        long Q = 1000000007;

        string[] inputX = Console.ReadLine().Split();

        for(long i = 0; i < N; i++)
        {
            BItemp = long.Parse(inputX[i]);
            Xsum += i * BItemp - (N - (i + 1)) * BItemp;
            Xsum %= Q;
        }

        string[] inputY = Console.ReadLine().Split();

        for (long i = 0; i < M; i++)
        {
            BItemp = long.Parse(inputY[i]);
            Ysum += i * BItemp - (M - (i + 1)) * BItemp;
            Ysum %= Q;
        }

        long ans = (Xsum * Ysum) % Q;
        Console.WriteLine(ans);
    }   
}