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#include <bits/stdc++.h>
#define dbg(x) cerr << #x << " = " << x << "\n"
using namespace std;
int n, m, res;
int tree[55];

int check(int a, int b) {
    //cout << a << " " << b << endl;
    if (a == b) return 0;
    int lele = 0;
    for (int i = a + 1; i < b - 1; i++) {
        if (tree[i] == tree[a] && check(i + 1, b)) {
            return 1;
        }
    }

    if (tree[a] == tree[b]) {
        return 1;
    }

    return 0;
}

int cnt, cnt2;
void b(int pos) {
    if (pos == n) {
        res += check(0, n-1);
        if (res == 1'000'000'007)
            res = 0;

        return;
    }

    for (int i = 1; i <= m; i++) {
        tree[pos] = i;
        b(pos + 1);
    }
}

using ll = long long;

const ll mod = 1000000007; // faster if const

ll modpow(ll b, ll e) {
	ll ans = 1;
	for (; e; b = b * b % mod, e /= 2)
		if (e & 1) ans = ans * b % mod;
	return ans;
}

#define rep(i, a, b) for(int i = a; i < (b); ++i)
vector<ll> berlekampMassey(vector<ll> s) {
	int n = s.size(), L = 0, m = 0;
	vector<ll> C(n), B(n), T;
	C[0] = B[0] = 1;

	ll b = 1;
	rep(i,0,n) { ++m;
		ll d = s[i] % mod;
		rep(j,1,L+1) d = (d + C[j] * s[i - j]) % mod;
		if (!d) continue;
		T = C; ll coef = d * modpow(b, mod-2) % mod;
		rep(j,m,n) C[j] = (C[j] - coef * B[j - m]) % mod;
		if (2 * L > i) continue;
		L = i + 1 - L; B = T; b = d; m = 0;
	}

	C.resize(L + 1); C.erase(C.begin());
	for (ll& x : C) x = (mod - x) % mod;
	return C;
}

ll a[3005];

int32_t main() {
    ios_base::sync_with_stdio(0);
    cin >> n >> m;
    if (n == 1) {
        cout << "0\n";
        return 0;
    }

    if (n == 2) {
        cout << m << "\n";
        return 0;
    }

    if (m == 1) {
        cout << 1 << "\n";
        return 0;
    }

    if (m == 2) {
        cout << ((2 + modpow(2, n) - 2 * n) % mod + mod) % mod << "\n";
        return 0;
    }

    if (n == 3) {
        cout << (m * m) % mod;
    }

    if (n == 4) {
        a[0] = 1; a[1] = 10; a[2] = 33; a[3] = 76;
        for (int i = 4; i < m; i++) {
            a[i] = ((4 * a[i-1] -6*a[i-2] +4*a[i-3] - a[i-4]) % mod + mod) % mod;
        }

        cout << a[m-1] << "\n";
        return 0;
    }

    b(0);
    cout << res << "\n";

}