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#pragma GCC optimize("O3,unroll-loops")
/* #pragma GCC target("inline-all-stringops,bmi,bmi2,popcnt,lzcnt") */
#pragma GCC target("inline-all-stringops,bmi,popcnt,lzcnt")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define pb push_back
#define mp make_pair
#define all(a) begin(a),end(a)
#define FOR(x,val,to) for(int x=(val);x<int((to));++x)
#define FORE(x,val,to) for(auto x=(val);x<=(to);++x)
#define FORR(x,arr) for(auto &x: arr)
#define FORS(x,plus,arr) for(auto x = begin(arr)+(plus); x != end(arr); ++x)
#define FORREV(x,plus,arr) for(auto x = (arr).rbegin()+(plus); x !=(arr).rend(); ++x)
#define REE(s_) {cout<<s_<<'\n';exit(0);}
#define GET(arr) for(auto &i: (arr)) sc(i)
#define whatis(x) cerr << #x << " is " << (x) << endl;
#define e1 first
#define e2 second
#define INF 0x7f7f7f7f
typedef std::pair<int,int> pi;
typedef std::vector<int> vi;
typedef std::vector<std::string> vs;
typedef int64_t ll;
typedef uint64_t ull;
#define umap unordered_map
#define uset unordered_set
using namespace std;
using namespace __gnu_pbds;

#ifdef ONLINE_JUDGE
#define whatis(x) ;
#endif
#ifdef _WIN32
#define getchar_unlocked() _getchar_nolock()
#define _CRT_DISABLE_PERFCRIT_LOCKS
#endif
template<class L, class R> ostream& operator<<(ostream &os, map<L, R> P) { for(auto const &vv: P)os<<"("<<vv.first<<","<<vv.second<<")"; return os; }
template<class T> ostream& operator<<(ostream &os, set<T> V) { os<<"[";for(auto const &vv:V)os<<vv<<","; os<<"]"; return os; }
template<class T> ostream& operator<<(ostream &os, vector<T> V) { os<<"[";for(auto const &vv:V)os<<vv<<","; os<<"]"; return os; }
template<class L, class R> ostream& operator<<(ostream &os, pair<L, R> P) { os<<"("<<P.first<<","<<P.second<<")"; return os; }
inline int fstoi(const string &str){auto it=str.begin();bool neg=0;int num=0;if(*it=='-')neg=1;else num=*it-'0';++it;while(it<str.end()) num=num*10+(*it++-'0');if(neg)num*=-1;return num;}
inline void getch(char &x){while(x = getchar_unlocked(), x < 33){;}}
inline void getstr(string &str){str.clear(); char cur;while(cur=getchar_unlocked(),cur<33){;}while(cur>32){str+=cur;cur=getchar_unlocked();}}
template<typename T> inline bool sc(T &num){ bool neg=0; int c; num=0; while(c=getchar_unlocked(),c<33){if(c == EOF) return false;} if(c=='-'){ neg=1; c=getchar_unlocked(); } for(;c>47;c=getchar_unlocked()) num=num*10+c-48; if(neg) num*=-1; return true;}template<typename T, typename ...Args> inline void sc(T &num, Args &...args){ bool neg=0; int c; num=0; while(c=getchar_unlocked(),c<33){;} if(c=='-'){ neg=1; c=getchar_unlocked(); } for(;c>47;c=getchar_unlocked()) num=num*10+c-48; if(neg) num*=-1; sc(args...); }
template<typename T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>; //s.find_by_order(), s.order_of_key() <- works like lower_bound
template<typename T> using ordered_map = tree<T, int, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define N 1000001

constexpr int md = 1000000007;

int main(){
    ios_base::sync_with_stdio(0);cin.tie(0);
    ll n,m;
    sc(n,m);
    ll actm = min(n, m);
    /* ll dp[n][actm + 1][2]; */
    ll dp[n + 1][actm + 1][2];
    ll sth[n + 1][actm + 1][2];
    memset(sth, 0, sizeof dp);
    memcpy(dp, sth, sizeof dp);
    dp[0][0][1] = 1;
    /* for(int i = 0; i < n - 1; ++i){ */
    for(int i = 0; i < n; ++i){
        for(int ilecnt = 0; ilecnt <= actm; ++ilecnt){
            for(int crtrue = 0; crtrue < 2; ++crtrue){
                /* whatis(i) */
                /* whatis(ilecnt) */
                /* whatis(crtrue) */
                /* whatis(dp[i][ilecnt][crtrue]) */
                /* for(int c = 0; c < actm; ++c){ */
                /* for(int c = 0; c < m; ++c){ */
                /*     /1* int nwcnt = ilecnt + (crtrue && c == ilecnt); *1/ */
                /*     int nwcnt = ilecnt + (crtrue && c >= ilecnt); */
                /*     if(nwcnt > actm) */
                /*         continue; */
                /*     int nwtrue = c < ilecnt; */
                /*     dp[i + 1][nwcnt][nwtrue] += dp[i][ilecnt][crtrue]; */
                /*     dp[i + 1][nwcnt][nwtrue] %= md; */
                /* } */
                /* dp[i + 1][ilecnt][1] += dp[i][ilecnt][crtrue] * max(0, ilecnt - 1); */
                dp[i + 1][ilecnt][1] += dp[i][ilecnt][crtrue] * ilecnt;
                dp[i + 1][ilecnt][1] %= md;
                if(ilecnt + crtrue <= actm){
                    dp[i + 1][ilecnt + crtrue][0] += dp[i][ilecnt][crtrue] * (m - ilecnt);
                    dp[i + 1][ilecnt + crtrue][0] %= md;
                }
            }
        }
    }
    ll res{};
    for(int i = 0; i <= actm; ++i){
        res += dp[n][i][1];
        res %= md;
    }
    /* for(int x = actm + 1; x <= m; ++x) */
    /*     res *= x; */
    /* for(int x = 1; x <= m - actm; ++x) */
    /*     res /= x; */
    cout << res << '\n';
}