#include <bits/stdc++.h>
using namespace std;
#define rep(i, n)  for(long long i=0;i<(long long)(n);i++)
#define REP(i,k,n) for(long long i=k;i<(long long)(n);i++)
#define all(a) a.begin(),a.end()
#define pb push_back
#define eb emplace_back
#define lb(v,k) (lower_bound(all(v),k)-v.begin())
#define ub(v,k) (upper_bound(all(v),k)-v.begin())
#define fi first
#define se second
#define pi M_PI
#define PQ(T) priority_queue<T>
#define SPQ(T) priority_queue<T,vector<T>,greater<T>>
#define dame(a) {out(a);return 0;}
#define decimal cout<<fixed<<setprecision(15);
typedef long long ll;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> PP;
typedef tuple<ll,ll,ll,ll> PPP;
typedef multiset<ll> S;
using vi=vector<ll>;
using vvi=vector<vi>;
using vvvi=vector<vvi>;
using vp=vector<P>;
using vvp=vector<vp>;
using vb=vector<bool>;
using vvb=vector<vb>;
const ll inf=1001001001001001001;
const int INF=1001001001;
const int mod=1000000007;
const double eps=1e-10;
template<class T> bool chmin(T&a,T b){if(a>b){a=b;return true;}return false;}
template<class T> bool chmax(T&a,T b){if(a<b){a=b;return true;}return false;}
template<class T> void out(T a){cout<<a<<'\n';}
template<class T> void outp(T a){cout<<'('<<a.fi<<','<<a.se<<')'<<'\n';}
template<class T> void outvp(T v){rep(i,v.size())cout<<'('<<v[i].fi<<','<<v[i].se<<')';cout<<'\n';}
template<class T> void outvvp(T v){rep(i,v.size())outvp(v[i]);}
template<class T> void outv(T v){rep(i,v.size()){if(i)cout<<' ';cout<<v[i];}cout<<'\n';}
template<class T> void outvv(T v){rep(i,v.size())outv(v[i]);}
template<class T> bool isin(T x,T l,T r){return (l)<=(x)&&(x)<=(r);}
template<class T> void yesno(T b){if(b)out("yes");else out("no");}
template<class T> void YesNo(T b){if(b)out("Yes");else out("No");}
template<class T> void YESNO(T b){if(b)out("YES");else out("NO");}
template<class T> void noyes(T b){if(b)out("no");else out("yes");}
template<class T> void NoYes(T b){if(b)out("No");else out("Yes");}
template<class T> void NOYES(T b){if(b)out("NO");else out("YES");}
void outs(ll a,ll b){if(a>=inf-100)out(b);else out(a);}
ll gcd(ll a,ll b){if(b==0)return a;return gcd(b,a%b);}
ll modpow(ll a,ll b){a%=mod;if(b==0)return 1;if(b&1)return a*modpow(a,b-1)%mod;ll k=modpow(a,b/2);return k*k%mod;}
vi seg;
ll N;
void init(ll n){
    N=1;
    while(N<n)N*=2;
    seg=vi(N*2-1);
}
void add(ll i,ll x){
    i=N+i-1;
    seg[i]+=x;
    seg[i]%=mod;
    while(i>0){
        i=(i-1)/2;
        seg[i]=seg[i*2+1]+seg[i*2+2];
    }
}
ll getsum(ll a,ll b,ll k,ll l,ll r){
    if(r<=a||b<=l)return 0;
    if(a<=l&&r<=b)return seg[k];
    ll c1=getsum(a,b,k*2+1,l,(l+r)/2);
    ll c2=getsum(a,b,k*2+2,(l+r)/2,r);
    return c1+c2;
}
int main(){
    ll n,m;cin>>n>>m;
    vi x(n),y(m);
    rep(i,n)cin>>x[i];
    rep(i,m)cin>>y[i];
    vp s;
    rep(i,n){
        if(x[i]<y[0]||x[i]>y[m-1])continue;
        ll k=lb(y,x[i]);
        s.eb(y[k]-x[i],y[k-1]-x[i]);
    }
    sort(all(s));
    s.erase(unique(all(s)),s.end());
    n=s.size();
    vi v(n);
    rep(i,n)v[i]=-s[i].se;
    vi t=v;sort(all(t));unique(all(t));
    //outv(v);
    vi id(n);
    rep(i,n)id[i]=lb(t,v[i])+1;
    //outv(id);
    init(t.size()+1);
    add(0,1);
    rep(i,n){
        add(id[i],getsum(0,id[i],0,0,N)%mod);
        //outv(seg);
    }
    out(getsum(0,N,0,0,N)%mod);
}

Measured memory_bytes: 7792