local function floorSum(n, m, a, b)
  local ans = 0LL
  while true do
    if m <= a then
      local v = a / m
      ans = ans + v * n * (n - 1LL) / 2LL
      a = a % m
    end
    if m <= b then
      ans = ans + (b / m) * n
      b = b % m
    end
    if a == 0LL then break end
    local y = (a * n + b) / m
    local z = (a * n + b) % m
    n, m, a, b = y, a, m, z
  end
  return ans
end

local n, m = io.read("*n", "*n")
local a, b = {}, {}
for i = 1, n do
  a[i] = io.read("*n") * 1LL
end
for i = 1, m do
  b[i] = io.read("*n") * 1LL
end
local mod = 1000000007LL
local ret = 0LL
for i = 1, n do
  for j = 1, m do
    local v = floorSum(b[j] + 1, b[j], a[i], 0LL)
    v = v % mod
    ret = (ret + v) % mod
  end
end
ret = (ret + ret) % mod
ret = tostring(ret):gsub("LL", "")
print(ret)

-- print(os.clock())