#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> P;
typedef pair<int,int> Pi;
#define rep(i,n) for(ll i=0;i<n;i++)
#define FOR(i,a,b) for(ll i=a;i<b;i++)
#define fi first
#define se second
#define endl "\n"

template<typename T> inline bool chmax(T &a, T b){if(a<b){a=b;return true;}return false;}
template<typename T> inline bool chmin(T &a, T b){if(a>b){a=b;return true;}return false;}
template<typename T> ostream& operator<<(ostream& s,const complex<T>& d) {return s<<"("<<d.real()<<", "<<d.imag()<< ")";}
template<typename T1, typename T2> ostream& operator<<(ostream& s,const pair<T1,T2>& d) {return s<<"("<<d.first<<", "<<d.second<<")";}
template<typename T> ostream& operator<<(ostream& s, const vector<T>& d){int len=d.size();rep(i,len){s<<d[i];if(i<len-1) s<<" ";}return s;}
template<typename T> ostream& operator<<(ostream& s,const vector<vector<T>>& d){int len=d.size();rep(i,len){s<<d[i]<<endl;}return s;}
template<typename T> ostream& operator<<(ostream& s,const set<T>& v){s<<"{ ";for(auto itr=v.begin();itr!=v.end();++itr) {if (itr!=v.begin()) {s<< ", ";}s<<(*itr);}s<<" }";return s;}
template<typename T1, typename T2> ostream& operator<<(ostream& s,const map<T1,T2>& m){s<<"{"<<endl;for(auto itr=m.begin();itr!=m.end();++itr){s<<" "<<(*itr).first<<" : "<<(*itr).second<<endl;}s<<"}"<<endl;return s;}

const ll mod=1e9+7;
const ll inf=1e17;
const int INF=1e9;
const double PI=acos(-1);
const double EPS=1e-10;

struct mint{
	ll x;
	mint(ll x=0):x((x%mod+mod)%mod){}
	friend ostream &operator<<(ostream& os,const mint& a){
		return os<<a.x;
	}
	friend istream &operator>>(istream& is,mint& a){
		ll t;
		is>>t;
		a=mint(t);
		return (is);
	}
	mint& operator+=(const mint a){
		if((x+=a.x)>=mod) x-=mod;
		return *this;
	}
	mint& operator-=(const mint a){
		if((x+=mod-a.x)>=mod)x-=mod;
		return *this;
	}
	mint& operator*=(const mint a){
		(x*=a.x)%=mod;
		return *this;
	}
	mint operator+(const mint a) const{
		mint res(*this);
		return res+=a;
	}
	mint operator-(const mint a) const{
		mint res(*this);
		return res-=a;
	}
	mint operator*(const mint a) const{
		mint res(*this);
		return res*=a;
	}
	mint pow(ll t) const{
		if (!t) return 1;
		mint a=pow(t>>1);
		a*=a;
		if(t&1) a*=*this;
		return a;
	}
	// for prime mod
	mint inv() const{
		return pow(mod-2);
	}
	mint& operator/=(const mint a){
		return (*this)*=a.inv();
	}
	mint operator/(const mint a) const{
		mint res(*this);
		return res/=a;
	}
};

struct combination{
  vector<mint> fact,ifact;
  combination(int n):fact(n+1),ifact(n+1){
	assert(n<mod);
	fact[0]=1;
	for(int i=1;i<=n;i++) fact[i]=fact[i-1]*i;
	ifact[n]=fact[n].inv();
	for(int i=n;i>=1;i--) ifact[i-1]=ifact[i]*i;
  }
  mint operator()(int n,int k){
	if (k<0 || k>n) return 0;
	return fact[n]*ifact[k]*ifact[n-k];
  }
};

int main(){
	cin.tie(0);ios::sync_with_stdio(false);
	int n,m;
	cin>>n>>m;
	mint ans=0;
	combination comb(n+m);
	rep(i,m+1){
		mint now=comb(m,i)*mint(i).pow(n);
		if((m-i)%2) now*=-1;
		ans+=now;
	}
	cout<<ans<<endl;
}