#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1000000007;
//https://judge.yosupo.jp/submission/5724
long long sum_of_floor_linear(long long a, long long b, long long c, long long n){
    long long tmp=b/c*n+a/c*n*(n-1)/2;
    if(a%c==0){
        return tmp;
    }
    long long next=(c-b%c+a%c-1)/(a%c);
    if(next>=n){
        return tmp;
    }
    a%=c;
    b=b%c+a*next;
    n-=next;
    return tmp+sum_of_floor_linear(c,n*a-((b+a*(n-1))/c*c-b),a,(b+a*(n-1))/c);
}
int main(){
  int N;
  cin >> N;
  int M;
  cin >> M;
  vector<long long> A(N);
  for (int i = 0; i < N; i++){
    cin >> A[i];
  }
  vector<long long> B(M);
  for (int i = 0; i < M; i++){
    cin >> B[i];
  }
  long long ans = 0;
  for (int i = 0; i < N; i++){
    for (int j = 0; j < M; j++){
      long long tmp = sum_of_floor_linear(A[i], A[i], B[j], B[j]);
      ans += tmp % MOD;
      ans %= MOD;
    }
  }
  ans *= 2;
  ans %= MOD;
  cout << ans << endl;
}