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>
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fr first
#define sc second
#define ll  long long
#define mp make_pair
#define mod 1000000007

using namespace std;

ll x[100100];
ll y[100100];

int main(){
    int n,m;
    cin>>n>>m;
    for(int i=0 ; i<n ; i++){
        scanf("%lld",&x[i]);
    }
    for(int i=0 ; i<m ; i++){
        scanf("%lld",&y[i]);
    }
    ll s = x[0];
    s %= mod;
    s += mod;
    s %= mod;

    ll r= 0;
    for(ll i=1 ;i<n ;i ++){
        ll r1 = (x[i]*i)%mod;
        r1 -= s;
        r1 %= mod;
        r1 += mod;
        r1 %= mod;
        r += r1;
        s += x[i];
        s %= mod;
        s += mod;
        s %= mod;
    }
    ll res = 0;
    s = y[0];
    s %= mod;
    s += mod;
    s %= mod;

    for(ll i=1 ;i<m ;i ++){
        ll r1 = (y[i]*i)%mod;
        r1 -= s;
        r1 %= mod;
        r1 += mod;
        r1 %= mod;
        res += (r*r1)%mod;
        res %= mod;
        s += y[i];
        s %= mod;
        s += mod;
        s %= mod;
    }
    cout<<res<<endl;

    return 0;
}