## https://yukicoder.me/problems/no/1201

from atcoder.math import floor_sum

MOD = 10 ** 9 + 7



def main():
    N = int(input())
    M = int(input())
    A = list(map(int, input().split()))
    B = list(map(int, input().split()))

    answer = 0
    for i in range(N):
        for j in range(M):
            ans = floor_sum(B[j] + 1, B[j], A[i], 0)
            answer += (2 * ans) % MOD
            answer %= MOD
    print(answer)




if __name__ == "__main__":
    main()