#include <bits/stdc++.h>

using namespace std;

#define int long long
// #define x first
// #define y second
#define File(a) freopen(a".in", "r", stdin), freopen(a".out", "w", stdout)

inline void debug() { cerr << '\n'; }
template<typename Type, typename... Other>
inline void debug(const Type& x, const Other&... y) { cerr << x << ' '; debug(y...); }
#define DEBUG(a...) cerr << "[" << #a << "] = ", debug(a);

typedef long long LL;
typedef pair<int, int> PII;

const int N = 2000010;
const int INF = 0x3f3f3f3f;
const int mod = 1e9 + 7;

template<typename Type>
inline void read(Type &res)
{
    res = 0;
    int ch = getchar(), flag = 0;
    while (!isdigit(ch)) flag |= ch == '-', ch = getchar();
    while (isdigit(ch)) res = (res << 3) + (res << 1) + (ch ^ 48), ch = getchar();
    res = flag ? -res : res;
}
template<typename Type, typename... Other>
inline void read(Type &res, Other&... y) { read(res), read(y...); }

int n, m;
int fc[N], f[N];

inline int ksm(int base, int k)
{
    int res = 1;
    while (k)
    {
        if (k & 1) res = res * base % mod;
        base = base * base % mod, k >>= 1;
    }
    return res;
}

inline int A(int m, int n) { return fc[m] * ksm(fc[m - n], mod - 2) % mod; }

void solve()
{
    read(n, m);
    f[0] = 1, f[1] = m - n;
    for (int i = 2; i <= n; i ++)
        f[i] = (f[i - 1] * (m - n) % mod + (i - 1) * (f[i - 1] + f[i - 2]) % mod) % mod;
    cout << A(m, n) * f[n] % mod << '\n';
}

signed main()
{
    for (int i = fc[0] = 1; i < N; i ++) fc[i] = fc[i - 1] * i % mod;
    solve();
    // int T; read(T);
    // while (T --) solve();
    return 0;
}