#include <bits/stdc++.h>
using namespace std;

using i32 = int;
using i64 = long long;

namespace zawa {

    template<long long mod>
    class modint {
    private:
        long long x;

    public:
        modint() : x(0) {}
        
        modint(long long x) : x((x % mod + mod) % mod) {}

        modint& operator+=(modint p) {
            x += p.x;
            if (x >= mod) x -= mod;
            return *this;
        }

        modint& operator-=(modint p) {
            x += mod - p.x;
            if (x >= mod) x -= mod;
            return *this;
        }

        modint& operator*=(modint p) {
            x = (1LL * x * p.x % mod);
            return *this;
        }

        modint& operator/=(modint p) {
            *this *= p.inv();
            return *this;
        }

        modint operator-() const {
            return modint(-x);
        }

        modint operator+(const modint& p) const {
            return modint(*this) += p;
        }

        modint operator-(const modint& p) const {
            return modint(*this) -= p;
        }

        modint operator*(const modint& p) const {
            return modint(*this) *= p;
        }

        modint operator/(const modint& p) const {
            return modint(*this) /= p;
        }

        long long val() {
            return x;
        }

        modint pow(long long p) {
            modint res(1), val(x);
            while(p) {
                if (p & 1) res *= val;
                val *= val;
                p >>= 1;
            }
            return res;
        }

        modint inv() {
            return pow(mod - 2);
        }
    };

}// namespace zawa

using mint = zawa::modint<1000000007>;

int main() {
    i64 n; cin >> n;
    i32 m; cin >> m;
    
    vector<mint> ps(m + 1);
    ps.front() = mint(1);
    for (i32 i = 1 ; i <= m ; i++) ps[i] = ps[i - 1] * i;

    mint ans = mint(m).pow(n);
    for (i32 i = 1 ; i <= m ; i++) {
        mint t = ps[m] / (ps[i] * ps[m - i]);
        t *= mint(m - i).pow(n);
        ans -= (i & 1 ? t : -t);
    }

    cout << ans.val() << endl;
}