using System; using System.Collections.Generic; using System.Linq; using System.IO; using System.Text; class Program { const int M = 1000000007; const double eps = 1e-9; static int[] dd = { 0, 1, 0, -1, 0 }; static void Main() { var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false }; var sc = new Scan(); var mt = new mymath(); long n; int m; sc.Multi(out n, out m); bool plus = true; long ans = 0; long cmb = 1; for (int i = m; i > 0; i--) { if (plus) { ans = (ans + mt.powmod(i, n, M) * cmb) % M; } else { ans = (ans - mt.powmod(i, n, M) * cmb) % M; } cmb = cmb * i % M * mt.powmod(m + 1 - i, M - 2, M) % M; plus = !plus; } sw.WriteLine((ans % M + M) % M); sw.Flush(); } static void swap(ref T a, ref T b) { var t = a; a = b; b = t; } static T[] copy(T[] a) { var ret = new T[a.Length]; for (int i = 0; i < a.Length; i++) ret[i] = a[i]; return ret; } static T[][] copy2(T[][] a) { var ret = new T[a.Length][]; for (int i = 0; i < a.Length; i++) { ret[i] = new T[a[0].Length]; for (int j = 0; j < a[0].Length; j++) ret[i][j] = a[i][j]; } return ret; } } class Scan { public int Int { get { return int.Parse(Str); } } public long Long { get { return long.Parse(Str); } } public string Str { get { return Console.ReadLine().Trim(); } } public int[] IntArr { get { return StrArr.Select(int.Parse).ToArray(); } } public int[] IntArrWithSep(char sep) { return Str.Split(sep).Select(int.Parse).ToArray(); } public long[] LongArr { get { return StrArr.Select(long.Parse).ToArray(); } } public double[] DoubleArr { get { return StrArr.Select(double.Parse).ToArray(); } } public string[] StrArr { get { return Str.Split(); } } public void Multi(out int a, out int b) { var arr = IntArr; a = arr[0]; b = arr[1]; } public void Multi(out int a, out int b, out int c) { var arr = IntArr; a = arr[0]; b = arr[1]; c = arr[2]; } public void Multi(out int a, out string b) { var arr = StrArr; a = int.Parse(arr[0]); b = arr[1]; } public void Multi(out string a, out int b) { var arr = StrArr; a = arr[0]; b = int.Parse(arr[1]); } public void Multi(out int a, out char b) { var arr = StrArr; a = int.Parse(arr[0]); b = arr[1][0]; } public void Multi(out char a, out int b) { var arr = StrArr; a = arr[0][0]; b = int.Parse(arr[1]); } public void Multi(out long a, out long b) { var arr = LongArr; a = arr[0]; b = arr[1]; } public void Multi(out long a, out int b) { var arr = LongArr; a = arr[0]; b = (int)arr[1]; } public void Multi(out int a, out long b) { var arr = LongArr; a = (int)arr[0]; b = arr[1]; } public void Multi(out string a, out string b) { var arr = StrArr; a = arr[0]; b = arr[1]; } } class mymath { public bool isprime(long a) { if (a < 2) return false; for (long i = 2; i * i <= a; i++) if (a % i == 0) return false; return true; } public long[][] powmat(long[][] A, long n, int M) { var E = new long[A.Length][]; for (int i = 0; i < A.Length; i++) { E[i] = new long[A.Length]; E[i][i] = 1; } if (n == 0) return E; var t = powmat(A, n / 2, M); if ((n & 1) == 0) return mulmat(t, t, M); return mulmat(mulmat(t, t, M), A, M); } public long[] mulmat(long[][] A, long[] x, int M) { var ans = new long[A.Length]; for (int i = 0; i < A.Length; i++) for (int j = 0; j < x.Length; j++) ans[i] = (ans[i] + x[j] * A[i][j]) % M; return ans; } public long[][] mulmat(long[][] A, long[][] B, int M) { var ans = new long[A.Length][]; for (int i = 0; i < A.Length; i++) { ans[i] = new long[B[0].Length]; for (int j = 0; j < B[0].Length; j++) for (int k = 0; k < B.Length; k++) ans[i][j] = (ans[i][j] + A[i][k] * B[k][j]) % M; } return ans; } public long powmod(long a, long b, long M) { if (a == 0) return 0; if (b == 0) return 1; var t = powmod(a, b / 2, M); if ((b & 1) == 0) return t * t % M; return t * t % M * a % M; } public long gcd(long a, long b) { while (b > 0) { var t = a % b; a = b; b = t; } return a; } public long lcm(long a, long b) { return a * (b / gcd(a, b)); } public long Comb(int n, int r) { const int M = 1000000007; if (n < 0 || r < 0 || r > n) return 0; if (n - r < r) r = n - r; if (r == 0) return 1; if (r == 1) return n; var numerator = new int[r]; var denominator = new int[r]; for (int k = 0; k < r; k++) { numerator[k] = n - r + k + 1; denominator[k] = k + 1; } for (int p = 2; p <= r; p++) { int pivot = denominator[p - 1]; if (pivot > 1) { int offset = (n - r) % p; for (int k = p - 1; k < r; k += p) { numerator[k - offset] /= pivot; denominator[k] /= pivot; } } } long result = 1; for (int k = 0; k < r; k++) if (numerator[k] > 1) result = result * numerator[k] % M; return result; } }