mod = 1000000007
eps = 10**-9


def main():
    import sys
    from math import gcd
    input = sys.stdin.readline

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

    ans = 0
    for a in A:
        for b in B:
            c, d = divmod(a, b)
            ans = (ans + ((c * b)%mod * (b+1))%mod)%mod
            if d != 0:
                ans = (ans + (d*2))%mod
                ans = (ans + ((d-1) * (b-1))%mod)%mod

                bb = b // gcd(b, d)
                ans = (ans + (b-1) // bb)%mod
    print(ans)


if __name__ == '__main__':
    main()