import sys
readline = sys.stdin.readline
MOD = 10**9+7

def gcd(a,b):
    while b:
        a, b = b, a%b
    return a

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

ans = 0
for a in A:
    for b in B:
        l = a//b
        ans = (ans + 2*l*b*(b+1)//2)%MOD
        k = a%b
        g = gcd(b, k)
        ans = (ans + 2*(k*(b+1)-b+g)//2)%MOD

print(ans)