#include <iostream>
#include <vector>
using namespace std;


// 素数 p で割ったあまりに関する構造体 (特に p = 1000000007 とすることが多い)
template<int MOD> struct Fp {
    long long val;
    constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
        if (val < 0) v += MOD;
    }
    constexpr int getmod() { return MOD; }
    constexpr Fp operator - () const noexcept {
        return val ? MOD - val : 0;
    }
    constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
    constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
    constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
    constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
    constexpr Fp& operator += (const Fp& r) noexcept {
        val += r.val;
        if (val >= MOD) val -= MOD;
        return *this;
    }
    constexpr Fp& operator -= (const Fp& r) noexcept {
        val -= r.val;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr Fp& operator *= (const Fp& r) noexcept {
        val = val * r.val % MOD;
        return *this;
    }
    constexpr Fp& operator /= (const Fp& r) noexcept {
        long long a = r.val, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b; swap(a, b);
            u -= t * v; swap(u, v);
        }
        val = val * u % MOD;
        if (val < 0) val += MOD;
        return *this;
    }
    constexpr bool operator == (const Fp& r) const noexcept {
        return this->val == r.val;
    }
    constexpr bool operator != (const Fp& r) const noexcept {
        return this->val != r.val;
    }
    friend constexpr ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept {
        return os << x.val;
    }
    friend constexpr istream& operator >> (istream &is, Fp<MOD>& x) noexcept {
        return is >> x.val;
    }
    friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
        if (n == 0) return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1) t = t * a;
        return t;
    }
};



// 二項係数ライブラリ
template<class T> struct BiCoef {
    vector<T> fact_, inv_, finv_;
    constexpr BiCoef(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1) {
        int MOD = fact_[0].getmod();
        for(int i = 2; i < n; i++){
            fact_[i] = fact_[i-1] * i;
            inv_[i] = -inv_[MOD%i] * (MOD/i);
            finv_[i] = finv_[i-1] * inv_[i];
        }
    }
    constexpr T com(int n, int k) const noexcept {
        if (n < k || n < 0 || k < 0) return 0;
        return fact_[n] * finv_[k] * finv_[n-k];
    }
    constexpr T fact(int n) const noexcept {
        if (n < 0) return 0;
        return fact_[n];
    }
    constexpr T inv(int n) const noexcept {
        if (n < 0) return 0;
        return inv_[n];
    }
    constexpr T finv(int n) const noexcept {
        if (n < 0) return 0;
        return finv_[n];
    }
};


// modint
using mint = Fp<1000000007>;
BiCoef<mint> bc(5100);

// ベル数
mint Bell(int n, int k) {
    if (k > n) k = n;
    vector<mint> jsum(k+2, 0);
    for (int j = 0; j <= k; ++j) {
        mint add = bc.finv(j);
        if (j % 2 == 0) jsum[j+1] = jsum[j] + add;
        else jsum[j+1] = jsum[j] - add;
    }
    mint res = 0;
    for (int i = 0; i <= k; ++i) {
        res += modpow(mint(i), n) * bc.finv(i) * jsum[k-i+1];
    }
    return res;
}

int main() {
    int n, k; cin >> n >> k;
    cout << Bell(n, k) << endl;
    
    /*
    // ベル数
    vector<mint> Bell(MAX+1, 0);
    Bell[0] = 1;
    for (int n = 0; n < MAX; ++n) {
        for (int i = 0; i <= n; ++i) {
            Bell[n+1] += bc.com(n, i) * Bell[i];
        }
    }

    // 答え
    int N; cin >> N;
    mint res = 0;
    for (int M = 0; M < N; ++M) res += bc.com(N, M) * Bell[M];
    cout << res << endl;
    */
}



Measured memory_bytes: 3248