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

lint sum_of_floor_linear(lint a,lint b,lint c,lint n){
    lint tmp=b/c*n+a/c*n*(n-1)/2;
    if(a%c==0){
        return tmp;
    }
    lint 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,m;cin>>n>>m;
  vector<int>a(n),b(m);
  const long long mod=1e9+7;
  for(int i=0;i<n;i++)cin>>a[i];
  for(int i=0;i<m;i++)cin>>b[i];
  long long ret=0;
  for(int i=0;i<n;i++){
    for(int j=0;j<m;j++){
      long long add=sum_of_floor_linear(a[i],0,b[j],b[j]+1);
      //cout<<i spa j spa sum_of_floor_linear(a[i],0,b[j],b[j]+1)<<endl;
      ret=(ret+add%mod*2)%mod;
    }
  }
  cout<<ret<<endl;
}