#include<iostream>
#include<vector>

const long long MOD = 1e9 + 7;

template<typename T, typename U>
T gcd(T a, U b){
  if(a < b){
    a ^= b;
    b ^= a;
    a ^= b;
  }

  T r;
  while(b){
    r = a % b;
    a = b;
    b = r;
  }

  return a;
}

template<typename T>
constexpr T inverse(T a, T m){
  T u = 0, v = 1;

  while(a){
    T t = m / a;
    m -= t * a; std::swap(a, m);
    u -= t * v; std::swap(u, v);
  }
  
  u %= MOD;
  if(u < 0) u += MOD;

  return u;
}

template<typename T>
constexpr T inverse(T a){
  return inverse(a, MOD);
}

using namespace std;

int main(){
  int N, M;
  cin >> N >> M;
  
  vector<long long> A(N), B(M);
  for(int i = 0; i < N; i++) cin >> A[i];
  for(int j = 0; j < M; j++) cin >> B[j];
  
  long long ans = 0;
  for(int i = 0; i < N; i++){
    for(int j = 0; j < M; j++){
      long long a = A[i], b = B[j];
      long long g = gcd(a, b);
      a /= g; b /= g;
      
      ans += a * B[j] % MOD * (B[j] + 1) % MOD * inverse(b) % MOD - (b - 1) * (B[j] / b) % MOD - (B[j] % b + 1) * (B[j] % b) % MOD * inverse(b) % MOD;
      ans %= MOD;
    }
  }
  
  cout << (ans + MOD) % MOD << endl;
  
  return 0;
}