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#include <vector>
#include <iostream>
#include <sstream>
#include <math.h>
#include <sys/time.h>
#include <cstdlib>
#include <algorithm>
#include <cassert>
#include <cstring>
#include <fstream>
#include <set>
#include <map>
#include <iomanip>
#include <queue>

#define FOR(i,a,b)  for(__typeof(b) i=(a);i<(b);++i)
#define REP(i,a)    FOR(i,0,a)
#define FOREACH(x,c)   for(__typeof(c.begin()) x=c.begin();x != c.end(); x++)
#define ALL(c)      c.begin(),c.end()
#define CLEAR(c)    memset(c,0,sizeof(c))
#define SIZE(c) (int) ((c).size())

#define PB          push_back
#define MP          make_pair
#define X           first
#define Y           second

#define ULL         unsigned long long
#define LL          long long
#define LD          long double
#define II         pair<int, int>
#define DD         pair<double, double>
#define FF          pair<float,float>

#define VC	    vector
#define VI          VC<int>
#define VVI         VC<VI>
#define VVVI        VC<VVI>
#define VD          VC<double>
#define VS          VC<string>
#define VII         VC<II>
#define VDD         VC<DD>
#define VFF         VC<FF>
#define VVD         VC<VD>
#define VVVD        VC<VVD>
#define VULL         VC<ULL>
#define VVULL VC<VULL>

#define DB(a)       cerr << #a << ": " << a << endl;

using namespace std;

template<class T> void print(VC < T > v) {cerr << "[";if (SIZE(v) != 0) cerr << v[0]; FOR(i, 1, SIZE(v)) cerr << "," << v[i]; cerr << "]\n";}
template<class T> string i2s(T &x) { ostringstream o; o << x; return o.str(); }
VS split(string &s, char c = ' ') {VS all; int p = 0, np; while (np = s.find(c, p), np >= 0) {all.PB(s.substr(p, np - p)); p = np + 1;} if (p < SIZE(s)) all.PB(s.substr(p)); return all;}

#define MOD 1000000007

int main(int argc, char *argv[]){
    int n,m;
    cin >> n >> m;
    VVULL O(n+1,VULL(n+1,0));
    VVULL C(n+1,VULL(n+1,0));
    C[0][0] = 1;
    FOR(i,1,n+1){
        int T = (i+1)/2;
        REP(t,T+1){ 
            O[i][t] += (O[i-1][t] * (m-t)) % MOD;
            C[i][t] += (O[i-1][t] * t) % MOD;
        
            if (t > 0)
                O[i][t] += (C[i-1][t-1] * (m-t+1)) % MOD;
            C[i][t] += (C[i-1][t] * t) % MOD;
            O[i][t] %= MOD;
            C[i][t] %= MOD;
        }
    }
    ULL s = 0;
    REP(t,(n+1)/2+1) s = (s + C[n][t])%MOD;
    cout << s << endl;
    return 0;
}