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

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

template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}
template<typename T> void drop(const T &x){cout<<x<<endl;exit(0);}
template<typename T=int>
vector<T> read(size_t n){
  vector<T> ts(n);
  for(size_t i=0;i<n;i++) cin>>ts[i];
  return ts;
}

// 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){
  using V = tuple<T, T, T, T>;
  static map<V, T> memo;
  if(memo.count(V(n,m,a,b))) return memo[V(n,m,a,b)];
  T &res=memo[V(n,m,a,b)];
  res=0;
  if(a>=m){
    res+=(n-1)*n*(a/m)/2;
    a%=m;
  }
  if(b>=m){
    res+=n*(b/m);
    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+=sum_of_floor(y,a,m,(a-x%a)%a);
  // cout<<(int)res<<endl;
  return res;
}

//INSERT ABOVE HERE
signed main(){
  cin.tie(0);
  ios::sync_with_stdio(0);
  int n,m;
  cin>>n>>m;
  auto as=read(n);
  auto bs=read(m);

  const int MOD = 1e9+7;
  int ans=0;
  for(int i=0;i<n;i++){
    for(int j=0;j<m;j++){
      ans+=sum_of_floor<long long>(bs[j]+1,bs[j],as[i],0)%MOD;
      ans%=MOD;
    }
  }

  ans*=2;
  ans%=MOD;
  cout<<ans<<newl;
  return 0;
}