import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }

struct ModInt(int M_) {
  import std.conv : to;
  alias M = M_;
  int x;
  this(ModInt a) { x = a.x; }
  this(long a) { x = cast(int)(a % M); if (x < 0) x += M; }
  ref ModInt opAssign(long a) { return (this = ModInt(a)); }
  ref ModInt opOpAssign(string op)(ModInt a) {
    static if (op == "+") { x += a.x; if (x >= M) x -= M; }
    else static if (op == "-") { x -= a.x; if (x < 0) x += M; }
    else static if (op == "*") { x = cast(int)((cast(long)(x) * a.x) % M); }
    else static if (op == "/") { this *= a.inv(); }
    else static assert(false);
    return this;
  }
  ref ModInt opOpAssign(string op)(long a) {
    static if (op == "^^") {
      if (a < 0) return (this = inv()^^(-a));
      ModInt t2 = this, te = ModInt(1);
      for (long e = a; e > 0; e >>= 1) {
        if (e & 1) te *= t2;
        t2 *= t2;
      }
      x = cast(int)(te.x);
      return this;
    } else return mixin("this " ~ op ~ "= ModInt(a)");
  }
  ModInt inv() const {
    int a = x, b = M, y = 1, z = 0, t;
    for (; ; ) {
      t = a / b; a -= t * b;
      if (a == 0) {
        assert(b == 1 || b == -1);
        return ModInt(b * z);
      }
      y -= t * z;
      t = b / a; b -= t * a;
      if (b == 0) {
        assert(a == 1 || a == -1);
        return ModInt(a * y);
      }
      z -= t * y;
    }
  }
  ModInt opUnary(string op: "-")() const { return ModInt(-x); }
  ModInt opBinary(string op, T)(T a) const {
    return mixin("ModInt(this) " ~ op ~ "= a");
  }
  ModInt opBinaryRight(string op)(long a) const {
    return mixin("ModInt(a) " ~ op ~ "= this");
  }
  bool opCast(T: bool)() const { return (x != 0); }
  string toString() const { return x.to!string; }
}

enum MO = 10^^9 + 7;
alias Mint = ModInt!MO;


void main() {
  try {
    for (; ; ) {
      const N = readInt();
      const M = readInt();
      
      auto dp = new Mint[][](N + 1, M + 1);
      dp[0][] = Mint(1);
      foreach (n; 1 .. N + 1) {
        Mint sum;
        foreach (m; 0 .. M + 1) {
          dp[n][m] = sum + (m + 1) * dp[n - 1][m];
          sum = sum * 2 + m * dp[n - 1][m];
        }
      }
      debug {
        if (N <= 10 && M <= 10) {
          foreach (n; 0 .. N + 1) {
            writeln(n, ": ", dp[n]);
          }
        }
      }
      writeln(dp[N][M]);
      
      debug {
        if (N <= 100 && M <= 100) {
          auto slow = new Mint[][](N + 1, M + 1);
          slow[0][] = Mint(1);
          foreach (n; 1 .. N + 1) {
            foreach (m; 0 .. M + 1) {
              // no 10
              slow[n][m] += (m + 1) * slow[n - 1][m];
              // 10
              foreach (i; 0 .. m) foreach (j; i + 1 .. m) {
                slow[n][m] += Mint(2)^^(j - i - 1) * slow[n - 1][m - (j - i)];
              }
            }
          }
          if (N <= 10 && M <= 10) {
            foreach (n; 0 .. N + 1) {
              writeln(n, ": ", slow[n]);
            }
          }
          writeln("slow[N][M] = ", slow[N][M]);
        }
      }
      
      debug {
        if (N <= 5 && M <= 5) {
          int brt;
          foreach (p; 0 .. (2^^N)^^M) {
            auto as = iota(M).map!(i => (p / (2^^N)^^i % 2^^N)).array;
            bool ok = true;
            foreach (i; 0 .. M) foreach (j; i + 1 .. M) {
              foreach_reverse (e; 0 .. N) {
                if (((as[i] >> e) & 1) && !((as[j] >> e) & 1)) {
                  ok = ok && !((as[i] ^ as[j]) & ((1 << e) - 1));
                  break;
                }
              }
            }
            if (ok) {
              ++brt;
            }
          }
          writeln("brt = ", brt);
        }
      }
    }
  } catch (EOFException e) {
  }
}


Measured memory_bytes: 102992