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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<bits/stdc++.h>
using namespace std;
#define mod 1000000000+7
#define ll long long
int main()
{
    int n,m;
    cin>>n>>m;
    int x[n],y[m],i,j;
    for(i=0;i<n;i++)
        cin>>x[i];
    for(j=0;j<m;j++)
        cin>>y[j];
    ll int are=0;
    for(i=0;i<n;i++)
    {
        for(j=i+1;j<n;j++)
        {
            for(int k=0;k<m;k++)
            {
                for(int l=k+1;l<m;l++)
                {
                    if(x[i]!=x[j]&&y[k]!=y[l])
                    {
                        are+=(abs(y[k]-y[l])*abs(x[i]-x[j]));
                        if(are>=mod)
                            are%=mod;
                    }
                }
            }
        }
    }
    cout<<are;
}