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#pragma GCC optimize ("Ofast")
#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
#define FOR(i, a, b) for (auto i=(a); i<(b); i++)
#define FORD(i, a, b) for (int i=(a); i>(b); i--)
#define SZ(x) ((int)(x).size())
#define ALL(x) (x).begin(), (x).end()
#define PPC(x) __builtin_popcountll(x)
#define MSB(x) (63 - __builtin_clzll(x))
#define LSB(x) __builtin_ctz(x)
#define ARG(x, i) (get<i>(x))
#define ithBit(m, i) ((m) >> (i) & 1)
#define pb push_back
#define ft first
#define sd second
#define kw(a) ((a) * (a))
#ifdef DEBUG
#include "debug.h"
#else
#define dbg(...) 0
#endif
using namespace std; 

template <typename T1, typename T2> inline void remin(T1& a, T2 b) { a = min(a, (T1)b);	}
template <typename T1, typename T2> inline void remax(T1& a, T2 b) { a = max(a, (T1)b);	}
 
const int maxN = 1 << 12, mod = 1'000'000'007;

template <typename T1, typename T2> inline void addMod(T1& a, T2 b) { a = (a + b) % mod; }
template <typename T1, typename T2> inline void multMod(T1& a, T2 b) { a = a * b % mod; }

long long good[2][maxN], all[2][maxN];

void solve()
{
	int n, m;
	scanf ("%d%d", &n, &m);
	all[0][0] = good[0][0] = 1;
	FOR(i, 1, n+1)
	{
		int s = i&1, r = s^1;
		good[s][0] = all[s][0] = 0;
		FOR(j, 1, min(m,i) + 1)
		{
			good[s][j] = all[r][j] * j % mod;
			
			all[s][j] = (all[r][j] - good[r][j] + mod) * m;
			all[s][j] += good[r][j] * j;
			all[s][j] += good[r][j-1] * (m-j+1);
			
			all[s][j] %= mod;
		}
	}
	
	long long res = 0;
	FOR(j, 1, min(n,m) + 1)
		res += good[n&1][j];
	res %= mod;
	printf("%lld\n", res);
}
 
int main()
{
	int t = 1;
	//scanf ("%d", &t);
	FOR(tid, 1, t+1)
	{
		//printf("Case #%d: ", tid);
		solve();
	}
	return 0;
}