#pragma GCC target ("sse4")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <bits/stdc++.h>
using namespace std;

using Int = long long;
const char newl = '\n';

const int MOD = 1e9+7;

// sum_{i=0}^{n-1} (ai + b) // m
// 0 <= a, b
template<typename T>
T sum_of_floor(T n,T m,T a,T b){
  T res=0;
  while(1){
    if(a>=m){
      res+=(n-1)*n*(a/m)/2;
      res%=MOD;
      a%=m;
    }
    if(b>=m){
      res+=n*(b/m);
      res%=MOD;
      b%=m;
    }

    T y=(a*n+b)/m;
    T x=y*m-b;
    if(y==0) return res;
    res+=(n-(x+a-1)/a)*y;
    res%=MOD;

    T nn=y;
    T nm=a;
    T na=m;
    T nb=(a-x%a)%a;

    n=nn;
    m=nm;
    a=na;
    b=nb;
  }
  return res;
}

//INSERT ABOVE HERE
const int MAX = 2020;
int as[MAX];
int bs[MAX];
signed main(){
  cin.tie(0);
  ios::sync_with_stdio(0);
  int n,m;
  cin>>n>>m;
  for(int i=0;i<n;i++) cin>>as[i];
  for(int j=0;j<m;j++) cin>>bs[j];

  vector<long long> ans(m);
  for(int i=0;i<n;i++){
    for(int j=0;j<m;j++){
      ans[j]+=sum_of_floor<long long>(bs[j]+1,bs[j],as[i],0);
      ans[j]%=MOD;
    }
  }

  long long res=0;
  for(int j=0;j<m;j++){
    res+=ans[j];
    res%=MOD;
  }
  res*=2;
  res%=MOD;
  cout<<res<<newl;
  return 0;
}