#include <bits/stdc++.h>

using namespace std;

const int N = 5e5+5, M = 1e6+6, OO = 0x3f3f3f3f;

typedef long long ll;
ll MOD = 1e9 + 7;

ll power(ll a, ll b){           // Fast Power O(log(b))
    if(!b)  return 1;
    ll t = power(a, b>>1);
    return t*t * (b&1 ? a : 1);
}

unsigned long long power(ll a, ll b, ll m){  // Fast power with mod;
    if(!b)  return 1;
    ll t = power(a, b>>1, m)%m;
    return ((t*t)%m * (b&1 ? a : 1)%m)%m;
}

ll gcd(ll a, ll b){
    if(!b)  return a;
    return gcd(b, a%b);
}

ll lcm(ll a, ll b){
//    return a*b/__gcd(a, b);
    return a/__gcd(a, b)*b;
}
 
ll mod(ll a, ll b){         // If you are modding negative values
    return (a%b + b)%b;
}
 
ll floor(ll a, ll b){ //Flooring with negative values
    return (a-mod(a, b))/b;
}
 
vector<ll> getDivisors(ll n){       //O(sqrt(n))
    vector<ll> ret;
    ll i;
    for(i = 1 ; i < n/i ; ++i){
        if(n%i == 0){
            ret.push_back(i);
            ret.push_back(n/i);
        }
    }
    if(i*i == n)    ret.push_back(i);
    return ret;
}
 
vector<ll> getMultiples(ll x, ll n){
    vector<ll> ret;
    for(ll m = x ; m <= n ; m += x)
        ret.push_back(m);
    return ret;
}
 
bool isPrime(ll n){             //O(sqrt(n))
    if(n < 2)   return 0;       //{0, 1}
    for(ll i = 2 ; i <= n/i ; ++i)
        if(n%i == 0)
            return 0;
    return 1;
}
 
// bool is_prime[N];
bitset<N> is_prime;
void sieve(){       //O(N*log(log(n))) ~= O(N)
    // fill(is_prime, is_prime+N, 1);       //with arrays
    is_prime.set();     //fills with 1
    is_prime[0] = is_prime[1] = 0;
    for(ll p = 2 ; p <= N/p ; ++p)
        if(is_prime[p])
            for(ll m = p*p ; m < N ; m += p)
                is_prime[m] = 0;
}
 
vector<pair<ll, ll>> factorize(ll n){
    vector<pair<ll, ll> > ret;
    for(ll p = 2 ; p <= n/p ; ++p){
        int e = 0;
        while(n%p == 0){
            n /= p;
            ++e;
        }
        if(e)   ret.push_back({p, e});
    }
    if(n > 1)   ret.push_back({n, 1});
    return ret;
}

unsigned long long fac[N];
unsigned long long modInverse(ll n, ll p) 
{ 
    return power(n, p-2, p); 
} 

unsigned long long nCrModPFermat(ll n, ll r, ll p) 
{ 
   // Base case 
   if (r==0 || r == n) 
      return 1; 
  
    // Fill factorial array so that we 
    // can find all factorial of r, n 
    // and n-r 
  
    return (fac[n]* modInverse(fac[r], p) % p * 
            modInverse(fac[n-r], p) % p) % p; 
} 
unsigned long long nprMod(ll n, ll r, ll p)
{
    if(n == r)
        return fac[n];
    if(r == 0)
        return 1;
    return (fac[n] * modInverse(fac[n-r], p)%p) %p;

    // cout<<n<<" "<<r<<endl;
    // cout<<nCrModPFermat(n, r, p)<<" "<<fac[r]<<endl;
    // return (nCrModPFermat(n, r, p) * fac[r]) % MOD;
}

int main(){
    fac[0] = 1;
    for(ll i = 1 ; i < N ; i++)
        fac[i] = (fac[i-1] %MOD * i % MOD) % MOD;
    unsigned long long n, m, ans = 0;
    scanf("%lld %lld", &n, &m);
    int flag = 1;
    for(int i = 0 ; i<= n ; i++)
    {
        ll x  = nprMod(m-i, n-i, MOD);
        ll tmp =  ((nCrModPFermat(n, i, MOD) * nprMod(m, i, MOD)) %MOD)  * (( x * x) % MOD) %MOD;
        // cout<<tmp<<endl;
        ans = (ans  + (tmp*flag) + MOD) %MOD;
        flag *= -1;
    }
    printf("%lld", ans%MOD);

    return 0;
}


Measured memory_bytes: 7660