#include <bits/stdc++.h>
using namespace std;
const double PI = 2 * acos(0.0);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());
const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";
template <class T0, class T1>
inline ostream &operator<<(ostream &out, pair<T0, T1> &a) {
  return out << "{" << a.first << ", " << a.second << "}";
}
template <class T0, class T1>
inline istream &operator>>(istream &in, pair<T0, T1> &a) {
  return in >> a.first >> a.second;
}
template <class T0, class T1, class T2>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2> &a) {
  return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a)
             << "}";
}
template <class T0, class T1, class T2, class T3>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2, T3> &a) {
  return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a)
             << ", " << get<3>(a) << "}";
}
template <class T>
inline ostream &operator<<(ostream &out, vector<T> &a) {
  out << "[";
  for (int i = 0; i < int(a.size()); ++i)
    out << a[i] << vector<string>{", ", "]  "}[i + 1 == a.size()];
  return out;
}
void smain();
signed main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  cout << setprecision(12) << fixed;
  smain();
  return 0;
}
const int M = 1e9 + 7;
int pw(int a, int n = M - 2) {
  int ret = 1;
  while (n) {
    if (n & 1) ret = (long long)ret * a % M;
    a = (long long)a * a % M;
    n >>= 1;
  }
  return ret;
}
const int N = 5050;
int dp[N][N];
void insum(int &a, int b) { a = (a + b) % M; }
void smain() {
  int n, m;
  cin >> n >> m;
  for (int j = 1; j <= m; ++j) {
    dp[n - 1][j] = pw(2, j);
  }
  for (int i = n - 2; i >= 0; --i) {
    ;
    for (int j = 1; j <= m; ++j) {
      insum(dp[i][j], (long long)dp[i + 1][j] * (j + 1) % M);
      dp[i + 1][j] = (long long)dp[i + 1][j] * j % M;
    };
    for (int j = 1; j <= m; ++j) {
      for (int k = 1; k < j; ++k) {
        insum(dp[i][j], (long long)dp[i + 1][k] * pw(2, j - k - 1) % M);
      }
    }
  }
  cout << dp[0][m];
}
