#include<cstdio>
using namespace std;
#pragma GCC optimize ("O3")
#pragma GCC target ("avx2")
#pragma GCC optimize("unroll-loops")

unsigned long long floor_sum(unsigned long long N,unsigned long long M,unsigned long long A,unsigned long long B)
//Sum[floor((A*i+B)/M),{i,0,N-1}]
{
	unsigned long long ans=0;
	if(A>=M)
	{
		unsigned long long AM=A/M;
		ans+=N*(N-1)/2*AM;
		A-=AM*M;
	}
	if(B>=M)
	{
		unsigned long long BM=B/M;
		ans+=N*BM;
		B-=BM*M;
	}
	unsigned long long Ym=(A*N+B)/M,Xm=Ym*M-B;
	if(Ym==0)return ans;
	unsigned long long TX=(Xm+A-1)/A;
	ans+=(N-TX)*Ym;
	ans+=floor_sum(Ym,A,M,TX*A-Xm);
	return ans;
}
int N,M;
int A[2000],B[2000];
main()
{
	scanf("%d%d",&N,&M);
	for(int i=0;i<N;i++)scanf("%d",&A[i]);
	for(int i=0;i<M;i++)scanf("%d",&B[i]);
	unsigned long ans=0;
	for(int i=0;i<N;i++)for(int j=0;j<M;j++)
	{
		ans+=2*floor_sum(B[j],B[j],A[i],A[i]);
		if(ans > 1e9+7)
		    ans%=(int)1e9+7;
	}
	printf("%lu\n",ans);
}