from math import gcd
mod = 10 ** 9 + 7


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

ans = 0
for b in B:
    for a in A:
        ans += a * (b + 1)
        ans -= b - gcd(a, b)
        ans %= mod

print(ans)