using System.Diagnostics;
using System;
using System.Linq;
using System.Numerics;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Text;
using static Functions;

using N = System.Int64;

static class Program
{
    static public void Main(string[] args)
    {
        Console.SetOut(new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false });
        var solver = new Solver();
        solver.Solve();
        Console.Out.Flush();
    }
}

public class Solver
{
    public void Solve()
    {
        int n = ri, m = ri;
        var pown = new ModInt[n + m + 1];
        var powm = new ModInt[n + m + 1];
        for (int i = 0; i < n + m + 1; i++)
        {
            pown[i] = new ModInt(i).Pow(n);
            powm[i] = new ModInt(i).Pow(m);
        }
        var f = new ModFrac(n + m + 1);
        var s = new ModInt[n + m + 1];
        for (int k = 1; k <= n + m; k++)
        {
            for (int l = 0; l <= k; l++)
                s[k] += f.fi[l] * f.fi[k - l] * pown[k - l] * powm[l];
            if ((k & 1) == 1) s[k] = -s[k];
        }
        var a = new ModInt[n + m + 1];
        for (int t = 2; t < n + m + 1; t++)
        {
            for (int k = 1; k <= t; k++)
                a[t] += s[k] * f.fi[t - k];
            a[t] *= f.f[t];
            if ((t & 1) == 1) a[t] = -a[t];
        }
        Write(Interpolate(a, new ModInt(5) / 2));
    }



    struct ModInt
    {
        private const long _mod = 1000000007;
        //private const long _mod = 998244353;
        long Val;
        public ModInt(long v) { Val = v; }
        public override string ToString() { return Val.ToString(); }
        public override bool Equals(object obj) => obj is ModInt other && this.Equals(other);
        public bool Equals(ModInt x) => Val == x.Val;
        public override int GetHashCode() => Val.GetHashCode();
        public static bool operator ==(ModInt a, ModInt b) { return a.Val == b.Val; }
        public static bool operator !=(ModInt a, ModInt b) { return a.Val != b.Val; }
        public static implicit operator ModInt(long n)
        {
            long r = n % _mod;
            return new ModInt(r < 0 ? r + _mod : r);
        }
        public static ModInt operator +(ModInt a, ModInt b)
        {
            long r = a.Val + b.Val;
            return new ModInt(r < _mod ? r : r - _mod);
        }
        public static ModInt operator -(ModInt a, ModInt b)
        {
            long r = a.Val - b.Val;
            return new ModInt(r < 0 ? r + _mod : r);
        }
        public static ModInt operator -(ModInt a) => new ModInt(a.Val == 0 ? 0 : _mod - a.Val);
        public static ModInt operator *(ModInt a, ModInt b) => new ModInt(a.Val * b.Val % _mod);
        public static ModInt operator /(ModInt a, ModInt b) => a * b.Inv;
        public ModInt Pow(long n)
        {
            long t = Val, r = 1;
            while (n > 0)
            {
                if ((n & 1) == 1) r = r * t % _mod;
                t = t * t % _mod;
                n >>= 1;
            }
            return new ModInt(r);
        }
        public ModInt Inv { get { return this.Pow(_mod - 2); } }
    }
    ModInt Interpolate(in ModInt[] a, ModInt x) // f(0),...,f(n-1)
    {
        int n = a.Length - 1;
        var f = new ModFrac(n);
        var s = new ModInt(n % 2 == 0 ? 1 : -1);
        ModInt g = 1;
        for (int i = 0; i <= n; i++) g *= x - i;
        ModInt ret = 0;
        for (int i = 0; i <= n; i++)
        {
            ModInt c = s * a[i] * f.fi[i] * f.fi[n - i];
            s *= -1;
            if (x == i)
            {
                ModInt p = 1;
                for (int j = 0; j < i; j++) p *= x - j;
                for (int j = i + 1; j <= n; j++) p *= x - j;
                ret += c * p;
            }
            else ret += c * g / (x - i);
        }
        return ret;
    }
    class ModFrac
    {
        public ModInt[] f;
        public ModInt[] fi;
        public ModFrac(long n)
        {
            f = new ModInt[n + 1];
            fi = new ModInt[n + 1];
            f[0] = 1;
            for (long i = 0; i < n; i++) f[i + 1] = f[i] * (i + 1);
            fi[n] = f[n].Inv;
            for (long i = n; i > 0; i--) fi[i - 1] = fi[i] * i;
        }
        public ModInt Binom(long n, long k)
        {
            if (n < 0) return 0;
            if (n == 0) return k == 0 ? 1 : 0;
            return 0 <= k && k <= n ? f[n] * fi[k] * fi[n - k] : 0;
        }
    }



    const long inf = (long)1 << 60;
    int ri { get { return (int)sc.Integer(); } }
    long rl { get { return sc.Integer(); } }
    double rd { get { return sc.Double(); } }
    string rs { get { return sc.Scan(); } }
    string rline { get { return sc.Line(); } }
    public StreamScanner sc = new StreamScanner(Console.OpenStandardInput());

    T[] RepArray<T>(T t, int count) => Enumerable.Repeat(t, count).ToArray();
    void WriteJoin<T>(string s, IEnumerable<T> t) { Console.WriteLine(string.Join(s, t)); }
    void WriteMax(params long[] x) => Console.Write(x.Max());
    void WriteMin(params long[] x) => Console.Write(x.Min());
    void Write<T>(T t) { Console.WriteLine(t.ToString()); }
    void WriteFlush<T>(T t) { Console.WriteLine(t.ToString()); Console.Out.Flush(); }
    void WriteError<T>(T t) { Console.Error.WriteLine(t.ToString()); }
    void YN(bool t) { Console.WriteLine(t ? "YES" : "NO"); }
    void Yn(bool t) { Console.WriteLine(t ? "Yes" : "No"); }
    void yn(bool t) { Console.WriteLine(t ? "yes" : "no"); }
}

public static class Functions
{
    public static int Popcount(long x)
    {
        x = x - ((x >> 1) & 0x5555555555555555);
        x = (x & 0x3333333333333333) + ((x >> 2) & 0x3333333333333333);
        x = (x + (x >> 4)) & 0x0f0f0f0f0f0f0f0f;
        x = x + (x >> 8);
        x = x + (x >> 16);
        x = x + (x >> 32);
        return (int)(x & 0x0000007f);
    }
    public static int Ctz(long x)
    {
        if (x == 0) return -1;
        return Popcount((x & -x) - 1);
    }
    public static int SafeMod(int x, int m)
    {
        int r = x % m;
        return r < 0 ? r + m : r;
    }
    public static long SafeMod(long x, long m)
    {
        long r = x % m;
        return r < 0 ? r + m : r;
    }
    public static long Floor(long a, long b) => a >= 0 ? a / b : (a + 1) / b - 1;
    public static long Ceil(long a, long b) => a > 0 ? (a - 1) / b + 1 : a / b;
    public static int Gcd(int a, int b) => b == 0 ? a : Gcd(b, a % b);
    public static long Gcd(long a, long b) => b == 0 ? a : Gcd(b, a % b);
    public static void Swap(ref int x, ref int y) { x ^= y; y ^= x; x ^= y; }
    public static void Swap(ref long x, ref long y) { x ^= y; y ^= x; x ^= y; }
    public static void Swap<T>(ref T x, ref T y) { T t = y; y = x; x = t; }
    public static T Clamp<T>(T x, T l, T r) where T : IComparable<T> => x.CompareTo(l) <= 0 ? l : (x.CompareTo(r) <= 0 ? x : r);
    public static void Chmin<T>(ref T x, T y) where T : IComparable<T> { if (x.CompareTo(y) > 0) x = y; }
    public static void Chmax<T>(ref T x, T y) where T : IComparable<T> { if (x.CompareTo(y) < 0) x = y; }
    public static int LowerBound<T, S>(in T[] list, S val, Func<T, S, int> comp)
    {
        if (list.Length == 0) return -1;
        int l = 0, r = list.Length;
        while (l < r)
        {
            int x = (l + r) / 2;
            if (comp(list[x], val) < 0) l = x + 1;
            else r = x;
        }
        return l;
    }
    public static int LowerBound<T, S>(in List<T> list, S val, Func<T, S, int> comp)
    {
        if (list.Count == 0) return -1;
        int l = 0, r = list.Count;
        while (l < r)
        {
            int x = (l + r) / 2;
            if (comp(list[x], val) < 0) l = x + 1;
            else r = x;
        }
        return l;
    }
    public static int UpperBound<T, S>(in List<T> list, S val, Func<T, S, int> comp)
    {
        if (list.Count == 0) return 0;
        if (comp(list.Last(), val) < 0) return list.Count;
        int l = 0, r = list.Count;
        while (l < r)
        {
            int x = (l + r) / 2;
            if (comp(list[x], val) <= 0) l = x + 1;
            else r = x;
        }
        return l;
    }
}

public class StreamScanner
{
    public StreamScanner(Stream stream) { str = stream; }
    private readonly Stream str;
    private readonly byte[] buf = new byte[1024];
    private int len, ptr;
    public bool isEof = false;
    public bool IsEndOfStream { get { return isEof; } }
    private byte read()
    {
        if (isEof) throw new EndOfStreamException();
        if (ptr >= len)
        {
            ptr = 0;
            if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; }
        }
        return buf[ptr++];
    }
    public char Char()
    {
        byte b = 0;
        do b = read();
        while (b < 33 || 126 < b);
        return (char)b;
    }
    public string Line()
    {
        var sb = new StringBuilder();
        for (var b = Char(); b != 10 && !isEof; b = (char)read()) sb.Append(b);
        return sb.ToString();
    }
    public string Scan()
    {
        var sb = new StringBuilder();
        for (var b = Char(); b >= 33 && b <= 126; b = (char)read()) sb.Append(b);
        return sb.ToString();
    }
    public long Integer()
    {
        long ret = 0; byte b = 0; var ng = false;
        do b = read();
        while (b != '-' && (b < '0' || '9' < b));
        if (b == '-') { ng = true; b = read(); }
        for (; true; b = read())
        {
            if (b < '0' || '9' < b) return ng ? -ret : ret;
            else ret = ret * 10 + b - '0';
        }
    }
    public double Double() { return double.Parse(Scan()); }
}