#include<cstdio> #include<cstdlib> #include<cstring> #include<cmath> //#include<cctype> #include<climits> #include<iostream> #include<string> #include<vector> #include<map> //#include<list> #include<queue> #include<deque> #include<algorithm> //#include<numeric> #include<utility> //#include<memory> #include<functional> #include<cassert> #include<set> #include<stack> #include<random> const int dx[] = {1, 0, -1, 0}; const int dy[] = {0, -1, 0, 1}; using namespace std; typedef long long ll; typedef unsigned long long ull; typedef vector<int> vi; typedef vector<ll> vll; typedef pair<int, int> pii; const int MOD = 1e9+7; ll mod_pow(ll x, ll p, ll MOD) { ll a = 1; while (p) { if (p%2) a = a*x%MOD; x = x*x%MOD; p/=2; } return a; } // mod_inverse ll mod_inverse(ll a, ll m) { return mod_pow(a, m-2, m); } const int MAXM = 100100; int H[MAXM]; ll fact[2*MAXM], rfact[2*MAXM]; ll nCr(int n, int r) { ll ret = fact[n]; (ret *= rfact[r]) %= MOD; (ret *= rfact[n-r]) %= MOD; return ret; } int main() { cin.tie(0); ios::sync_with_stdio(false); fact[0] = rfact[0] = 1; for (int i = 1; i < 2*MAXM; i++) { fact[i] = (fact[i-1]*i)%MOD; rfact[i] = mod_inverse(fact[i], MOD); } ll N; int M; cin >> N >> M; if (N < M) { cout << 0 << endl; return 0; } ll ans = 0; for (int i = 1; i <= M; i++) { ll tmp = nCr(M, i) * mod_pow(i, N, MOD)%MOD; if ((M-i)%2 == 0) ans += tmp; else ans -= tmp; ans = (ans+MOD)%MOD; } cout << ans << endl; return 0; }