#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#define rep2(i, m, n) for (int i = (m); i < (n); ++i)
#define rep(i, n) rep2(i, 0, n)
#define drep2(i, m, n) for (int i = (m)-1; i >= (n); --i)
#define drep(i, n) drep2(i, n, 0)
#define all(a) (a).begin(), (a).end()
template<typename T = int> using V = vector<T>;
template<typename T = int> using P = pair<T, T>;
using Vi = V<int>;
using Vl = V<ll>;
using Vd = V<ld>;
using Vb = V<bool>;
using VVi = V<Vi>;
using VVl = V<Vl>;
using VVb = V<Vb>;
using Pi = P<int>;
using Pl = P<ll>;
using Pd = P<ld>;
template<typename T> vector<T> make_vec(size_t n, T a) { return vector<T>(n, a); }
template<typename... Ts> auto make_vec(size_t n, Ts... ts) { return vector<decltype(make_vec(ts...))>(n, make_vec(ts...)); }
template<typename T> inline int sz(T &x) { return x.size(); }
template<typename T> inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; }
template<typename T> inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; }
template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { is >> p.first >> p.second; return is; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p) { os << '(' << p.first << ", " << p.second << ')'; return os; }
template<typename T> istream &operator>>(istream &is, vector<T> &v) { for (auto &e : v) is >> e; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &v) { for (auto &e : v) os << e << ' '; return os; }
template<typename T> inline int count_between(vector<T> &a, T l, T r) { return lower_bound(all(a), r) - lower_bound(all(a), l); } // [l, r)
inline int fLog2(const ll x) { assert(x > 0); return 63-__builtin_clzll(x); } // floor(log2(x))
inline int cLog2(const ll x) { assert(x > 0); return (x == 1) ? 0 : 64-__builtin_clzll(x-1); } // ceil(log2(x))
inline int popcount(const ll x) { return __builtin_popcountll(x); }
inline void fail() { cout << -1 << '\n'; exit(0); }
struct fast_ios { fast_ios(){ cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
// const int INF  = 1<<30;
// const ll INFll = 1ll<<60;
// const ld EPS   = 1e-10;
// const ld PI    = acos(-1.0);
const int MOD  = int(1e9)+7;
// const int MOD  = 998244353;


template<int MOD> struct ModInt {
  int x;
  ModInt(ll _x = 0) : x( (0 <= _x && _x < MOD) ? _x : (_x%MOD+MOD)%MOD ) {}
  constexpr int &value() noexcept { return x; }
  constexpr ModInt operator-() const noexcept { return ModInt(MOD-x); }
  constexpr ModInt operator+(const ModInt y) const noexcept { return ModInt(*this) += y; }
  constexpr ModInt operator-(const ModInt y) const noexcept { return ModInt(*this) -= y; }
  constexpr ModInt operator*(const ModInt y) const noexcept { return ModInt(*this) *= y; }
  constexpr ModInt operator/(const ModInt y) const noexcept { return ModInt(*this) /= y; }
  constexpr ModInt &operator+=(const ModInt y) noexcept { x += y.x; if (x >= MOD) x -= MOD; return *this; }
  constexpr ModInt &operator-=(const ModInt y) noexcept { x -= y.x; if (x < 0) x += MOD; return *this; }
  constexpr ModInt &operator*=(const ModInt y) noexcept { x = ll(x) * y.x % MOD; return *this; }
  constexpr ModInt &operator/=(const ModInt y) {
    int a = y.x, b = MOD, u = 1, v = 0;
    while (b) {
      int t = a / b;
      a -= t * b; swap(a, b);
      u -= t * v; swap(u, v);
    }
    x = ll(x) * u % MOD;
    if (x < 0) x += MOD;
    return *this;
  }
  constexpr ModInt pow(ll n) const noexcept {
    ModInt x(1);
    ModInt a = *this;
    for (; n > 0; n >>= 1, a *= a) if (n&1) x *= a;
    return x;
  }
};
using mint = ModInt<MOD>;
using Vm = vector<mint>;
// using VVm = vector<Vm>;
// using VVVm = vector<VVm>;
// istream &operator>>(istream &is, mint &a) { return is >> a.x; }
ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }


// compress vector
template<typename T>
pair<map<T, int>, vector<T>> compress(vector<T> v) {
  sort(all(v));
  v.erase(unique(all(v)), v.end());
  map<T, int> zip;
  rep(i, sz(v)) zip[v[i]] = i;
  return {move(zip), move(v)};
}


template<typename T>
struct FenwickTree {
  int n; vector<T> d;
  FenwickTree(int n = 0) : n(n), d(n+1) {}
  void add(int i, T a = 1) { for (++i; i <= n; i += i & -i) d[i] += a; }
  T sum(int i) { T x = 0; for (; i > 0; i -= i & -i) x += d[i]; return x; }
  T sum(int l, int r) { return sum(r) - sum(l); } // [l, r)
  T operator[](const int i) { return sum(i, i+1); }
  int lower_bound(T x) { // the smallest k (0-indexed) such that sum of ft[0, k) >= x
    if (x <= 0) return 0;
    int l = 0;
    for (int i = 1<<fLog2(n); i > 0; i >>= 1) {
      if (l+i <= n && d[l+i] < x) l += i, x -= d[l];
    }
    return l+1;
  }
  int get(int k) { return lower_bound(k+1) - 1; } // the k-th (0-indexed) smallest element
};


int main() {
  int n, m; cin >> n >> m;
  Vi x(n), y(m); cin >> x >> y;

  V<Pi> lr = {{0, 0}};
  Vi ls(1), rs(1);
  rep(i, n) {
    auto it = lower_bound(all(y), x[i]);
    if (it == y.begin() || it == y.end()) continue;
    int r = *it - x[i];
    int l = x[i] - *(--it);
    lr.emplace_back(l, r);
    ls.push_back(l);
    rs.push_back(r);
  }

  auto [zl, _l] = compress(ls);
  auto [zr, _r] = compress(rs);
  int k = sz(zl);

  VVi a(k);
  for (auto [l, r] : lr) a[zl[l]].push_back(zr[r]);
  for (auto &e : a) {
  }

  FenwickTree<mint> dp(n+1);
  dp.add(0);
  mint ans = 1;

  for (auto &e : a) {
    sort(all(e));
    e.erase(unique(all(e)), e.end());
    reverse(all(e));
    for (auto x : e) {
      mint y = dp.sum(x);
      dp.add(x, y);
      ans += y;
    }
  }
  cout << ans << '\n';
}


Measured memory_bytes: 21240