#include <bits/stdc++.h>
#pragma GCC diagnostic ignored "-Wsign-compare"
#pragma GCC diagnostic ignored "-Wsign-conversion"
#define NDEBUG
#define SHOW(...) static_cast<void>(0)
//!===========================================================!//
//!  dP     dP                          dP                    !//
//!  88     88                          88                    !//
//!  88aaaaa88a .d8888b. .d8888b. .d888b88 .d8888b. 88d888b.  !//
//!  88     88  88ooood8 88'  '88 88'  '88 88ooood8 88'  '88  !//
//!  88     88  88.  ... 88.  .88 88.  .88 88.  ... 88        !//
//!  dP     dP  '88888P' '88888P8 '88888P8 '88888P' dP        !//
//!===========================================================!//
template <typename T, typename A>
std::istream& operator>>(std::istream& is, std::vector<T, A>& v)
{
    for (auto& e : v) { is >> e; }
    return is;
}
template <typename T>
T read()
{
    T v;
    return std::cin >> v, v;
}
template <typename T>
std::vector<T> readVec(const std::size_t l)
{
    std::vector<T> v(l);
    for (auto& e : v) { std::cin >> e; }
    return v;
}
using ld = long double;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
constexpr unsigned int MOD = 1000000007;
template <typename T>
constexpr T INF = std::numeric_limits<T>::max() / 4;
template <typename F>
constexpr F PI = static_cast<F>(3.1415926535897932385);
std::mt19937 mt{std::random_device{}()};
template <typename T>
bool chmin(T& a, const T& b) { return (a > b ? a = b, true : false); }
template <typename T>
bool chmax(T& a, const T& b) { return (a < b ? a = b, true : false); }
template <typename T>
std::vector<T> Vec(const std::size_t n, T v) { return std::vector<T>(n, v); }
template <class... Args>
auto Vec(const std::size_t n, Args... args) { return std::vector<decltype(Vec(args...))>(n, Vec(args...)); }
template <typename T>
constexpr T popCount(const T u)
{
#ifdef __has_builtin
    return u == 0 ? T(0) : (T)__builtin_popcountll(u);
#else
    unsigned long long v = static_cast<unsigned long long>(u);
    return v = (v & 0x5555555555555555ULL) + (v >> 1 & 0x5555555555555555ULL), v = (v & 0x3333333333333333ULL) + (v >> 2 & 0x3333333333333333ULL), v = (v + (v >> 4)) & 0x0F0F0F0F0F0F0F0FULL, static_cast<T>(v * 0x0101010101010101ULL >> 56 & 0x7f);
#endif
}
template <typename T>
constexpr T log2p1(const T u)
{
#ifdef __has_builtin
    return u == 0 ? T(0) : T(64 - __builtin_clzll(u));
#else
    unsigned long long v = static_cast<unsigned long long>(u);
    return v = static_cast<unsigned long long>(v), v |= (v >> 1), v |= (v >> 2), v |= (v >> 4), v |= (v >> 8), v |= (v >> 16), v |= (v >> 32), popCount(v);
#endif
}
template <typename T>
constexpr T clog(const T v) { return v == 0 ? T(0) : log2p1(v - 1); }
template <typename T>
constexpr T msbp1(const T v) { return log2p1(v); }
template <typename T>
constexpr T lsbp1(const T v)
{
#ifdef __has_builtin
    return __builtin_ffsll(v);
#else
    return v == 0 ? T(0) : popCount((v & (-v)) - T(1)) + T(1);
#endif
}
template <typename T>
constexpr bool ispow2(const T v) { return popCount(v) == 1; }
template <typename T>
constexpr T ceil2(const T v) { return v == 0 ? T(1) : T(1) << log2p1(v - 1); }
template <typename T>
constexpr T floor2(const T v) { return v == 0 ? T(0) : T(1) << (log2p1(v) - 1); }
//!===================================================================!//
//!  .d88888b                    d888888P                             !//
//!  88.    "'                      88                                !//
//!  'Y88888b. .d8888b. .d8888b.    88    88d888b. .d8888b. .d8888b.  !//
//!        '8b 88ooood8 88'  '88    88    88'  '88 88ooood8 88ooood8  !//
//!  d8'   .8P 88.  ... 88.  .88    88    88       88.  ... 88.  ...  !//
//!   Y88888P  '88888P' '8888P88    dP    dP       '88888P' '88888P'  !//
//!                          .88                                      !//
//!                      d8888P                                       !//
//!===================================================================!//
template <typename ValMonoid>
class SegTree
{
public:
    using ValType = typename ValMonoid::ValType;
    SegTree(const std::size_t N, const ValType initial = ValMonoid::id()) : size(N), half(ceil2(size)), val(half << 1, ValMonoid::id())
    {
        if (initial != ValMonoid::id()) {
            std::fill(val.begin() + half, val.end(), initial);
            for (std::size_t i = half - 1; i >= 1; i--) { up(i); }
        }
    }
    template <typename InIt>
    SegTree(const InIt first, const InIt last) : size(std::distance(first, last)), half(ceil2(size)), val(half << 1, ValMonoid::id())
    {
        std::copy(first, last, val.begin() + half);
        for (std::size_t i = half - 1; i >= 1; i--) { up(i); }
    }
    ValType get(const std::size_t a) const { return assert(a < size), val[a + half]; }
    void set(std::size_t a, const ValType& v)
    {
        assert(a < size);
        val[a += half] = v;
        while (a >>= 1) { up(a); }
    }
    ValType fold(std::size_t L, std::size_t R) const
    {
        assert(L < R), assert(R <= size);
        ValType accl = ValMonoid::id(), accr = ValMonoid::id();
        for (L += half, R += half; L < R; L >>= 1, R >>= 1) {
            if (L & 1) { accl = acc(accl, val[L++]); }
            if (R & 1) { accr = acc(val[--R], accr); }
        }
        return acc(accl, accr);
    }
    friend std::ostream& operator<<(std::ostream& os, const SegTree& seg)
    {
        os << "[";
        for (std::size_t i = seg.half; i < seg.half + seg.size; i++) { os << seg.val[i] << (i + 1 == seg.half + seg.size ? "" : ","); }
        return (os << "]\n");
    }

private:
    void up(const std::size_t i) { val[i] = acc(val[i << 1], val[i << 1 | 1]); }
    const std::size_t size, half;
    std::vector<ValType> val;
    const ValMonoid acc{};
};
//!=================================!//
//!  .d88888b                       !//
//!  88.    "'                      !//
//!  'Y88888b. dP    dP 88d8b.d8b.  !//
//!        '8b 88    88 88''88''88  !//
//!  d8'   .8P 88.  .88 88  88  88  !//
//!   Y88888P  '88888P' dP  dP  dP  !//
//!=================================!//
template <typename ElemType>
struct Sum
{
    using ValType = ElemType;
    ValType operator()(const ValType& a, const ValType& b) const { return a + b; }
    static constexpr ValType id() { return ValType{}; }
};
//!===============================================================!//
//!   88888888b            dP       .88888.   a88888b. 888888ba   !//
//!   88                   88      d8'   '88 d8'   '88 88    '8b  !//
//!  a88aaaa    dP.  .dP d8888P    88        88        88     88  !//
//!   88         '8bd8'    88      88   YP88 88        88     88  !//
//!   88         .d88b.    88      Y8.   .88 Y8.   .88 88    .8P  !//
//!   88888888P dP'  'dP   dP       '88888'   Y88888P' 8888888P   !//
//!===============================================================!//
template <typename T>
constexpr std::pair<T, T> extgcd(const T a, const T b)
{
    if (b == 0) { return std::pair<T, T>{1, 0}; }
    const auto p = extgcd(b, a % b);
    return {p.second, p.first - p.second * (a / b)};
}
template <typename T>
constexpr T inverse(const T a, const T mod) { return (mod + extgcd((mod + a % mod) % mod, mod).first % mod) % mod; }
//!========================================================!//
//!  8888ba.88ba                 dP    dP            dP    !//
//!  88  '8b  '8b                88    88            88    !//
//!  88   88   88 .d8888b. .d888b88    88 88d888b. d8888P  !//
//!  88   88   88 88'  '88 88'  '88    88 88'  '88   88    !//
//!  88   88   88 88.  .88 88.  .88    88 88    88   88    !//
//!  dP   dP   dP '88888P' '88888P8    dP dP    dP   dP    !//
//!========================================================!//
template <uint mod>
class ModInt
{
private:
    uint v;
    static uint norm(const uint& x) { return x < mod ? x : x - mod; }
    static ModInt make(const uint& x)
    {
        ModInt m;
        return m.v = x, m;
    }
    static ModInt power(ModInt x, ll n)
    {
        ModInt ans = 1;
        for (; n; n >>= 1, x *= x) {
            if (n & 1) { ans *= x; }
        }
        return ans;
    }
    static ModInt inv(const ModInt& x) { return ModInt{inverse((ll)x.v, (ll)mod)}; }

public:
    ModInt() : v{0} {}
    ModInt(const ll val) : v{norm(uint(val % (ll)mod + (ll)mod))} {}
    ModInt(const ModInt<mod>& n) : v{n()} {}
    explicit operator bool() const { return v != 0; }
    ModInt<mod>& operator=(const ModInt<mod>& n) { return v = n(), (*this); }
    ModInt<mod>& operator=(const ll val) { return v = norm(uint(val % (ll)mod + (ll)mod)), (*this); }
    ModInt<mod> operator+() const { return *this; }
    ModInt<mod> operator-() const { return make(norm(mod - v)); }
    ModInt<mod> operator+(const ModInt<mod>& val) const { return make(norm(v + val())); }
    ModInt<mod> operator-(const ModInt<mod>& val) const { return make(norm(v + mod - val())); }
    ModInt<mod> operator*(const ModInt<mod>& val) const { return make((uint)((ll)v * val() % (ll)mod)); }
    ModInt<mod> operator/(const ModInt<mod>& val) const { return *this * inv(val()); }
    ModInt<mod>& operator+=(const ModInt<mod>& val) { return *this = *this + val; }
    ModInt<mod>& operator-=(const ModInt<mod>& val) { return *this = *this - val; }
    ModInt<mod>& operator*=(const ModInt<mod>& val) { return *this = *this * val; }
    ModInt<mod>& operator/=(const ModInt<mod>& val) { return *this = *this / val; }
    ModInt<mod> operator+(const ll val) const { return ModInt{v + val}; }
    ModInt<mod> operator-(const ll val) const { return ModInt{v - val}; }
    ModInt<mod> operator*(const ll val) const { return ModInt{(ll)v * (val % mod)}; }
    ModInt<mod> operator/(const ll val) const { return ModInt{(ll)v * inv(val)}; }
    template <typename I>
    ModInt<mod> operator^(const I n) const { return power(v, n); }
    ModInt<mod>& operator+=(const ll val) { return *this = *this + val; }
    ModInt<mod>& operator-=(const ll val) { return *this = *this - val; }
    ModInt<mod>& operator*=(const ll val) { return *this = *this * val; }
    ModInt<mod>& operator/=(const ll val) { return *this = *this / val; }
    template <typename I>
    ModInt<mod>& operator^=(const I n) { return (*this) = ((*this) ^ n); }
    bool operator==(const ModInt<mod>& val) const { return v == val.v; }
    bool operator!=(const ModInt<mod>& val) const { return not(*this == val); }
    bool operator==(const ll val) const { return v == norm(uint((ll)mod + val % (ll)mod)); }
    bool operator!=(const ll val) const { return not(*this == val); }
    uint operator()() const { return v; }
};
template <uint mod>
inline ModInt<mod> operator+(const ll val, const ModInt<mod>& n) { return n + val; }
template <uint mod>
inline ModInt<mod> operator-(const ll val, const ModInt<mod>& n) { return ModInt<mod>{val - (ll)n()}; }
template <uint mod>
inline ModInt<mod> operator*(const ll val, const ModInt<mod>& n) { return n * val; }
template <uint mod>
inline ModInt<mod> operator/(const ll val, const ModInt<mod>& n) { return ModInt<mod>(val) / n; }
template <uint mod>
inline bool operator==(const ll val, const ModInt<mod>& n) { return n == val; }
template <uint mod>
inline bool operator!=(const ll val, const ModInt<mod>& n) { return not(val == n); }
template <uint mod>
inline std::istream& operator>>(std::istream& is, ModInt<mod>& n)
{
    uint v;
    return is >> v, n = v, is;
}
template <uint mod>
std::ostream& operator<<(std::ostream& os, const ModInt<mod>& n) { return (os << n()); }
//!============================================!//
//!    8888ba.88ba             oo              !//
//!    88  '8b  '8b                            !//
//!    88   88   88  .d8888b.  dP  88d888b.    !//
//!    88   88   88  88'  '88  88  88'  '88    !//
//!    88   88   88  88.  .88  88  88    88    !//
//!    dP   dP   dP  '88888P8  dP  dP    dP    !//
//!============================================!//
int main()
{
    using mint = ModInt<MOD>;
    const int N = read<int>(), M = read<int>();
    const auto xs = readVec<int>(N), ys = readVec<int>(M);
    std::vector<int> ls, rs;
    std::map<int, int> rzip;
    rzip[0] = 0;
    for (const int x : xs) {
        if (x < ys.front() or ys.back() < x) { continue; }
        const auto it = std::lower_bound(ys.begin(), ys.end(), x);
        const int R = *it - x, L = x - *(it - 1);
        rs.push_back(R), ls.push_back(L), rzip[R] = 0;
    }
    if (rs.empty()) { return std::cout << 1 << std::endl, 0; }
    int cnt = 0;
    for (auto& p : rzip) { p.second = cnt++; }
    for (auto& r : rs) { r = rzip[r]; }
    std::map<int, std::set<int, std::greater<int>>> dist;
    for (int i = 0; i < ls.size(); i++) { dist[ls[i]].insert(rs[i]); }
    const int S = rzip.size();
    SegTree<Sum<mint>> dp(S);
    dp.set(0, 1);
    for (const auto& st : dist) {
        for (const int r : st.second) { dp.set(r, dp.get(r) + dp.fold(0, r)); }
    }
    std::cout << dp.fold(0, S) << std::endl;
    return 0;
}


Measured memory_bytes: 20976