import std;

int readInt() {
	int x;
	readf!" %d"(x);
	return x;
}
int[] readArray(int n) {
	auto a = new int[](n);
	return a.map!(i => readInt).array;
}

immutable long P = (1e9 + 7).to!long;
struct Combinatorics(long P) {
	long[] inv, fac, ifac;
	this(int n) {
		inv = new long[](n + 1);
		fac = new long[](n + 1);
		ifac = new long[](n + 1);
		inv[1] = fac[0] = ifac[0] = 1;
		for(int i = 2; i <= n; i ++)
			inv[i] = (P - P / i) * inv[P % i] % P;
		for(int i = 1; i <= n; i ++) {
			fac[i] = i * fac[i - 1] % P;
			ifac[i] = inv[i] * ifac[i - 1] % P;
		}
	}
	long binom(int n, int m) {
		if(n < m || m < 0) return 0; // n >= 0
		return fac[n] * ifac[m] % P * ifac[n - m] % P;
	}
	long qpow(long a, long b) {
		long r = 1, t = a % P;
		for(; b; b /= 2) {
			if(b & 1)
				r = r * t % P;
			t = t * t % P;
		}
		return r;
	}
};

void main() {
	int n = readInt, m = readInt;
	
	auto comb = new Combinatorics!P(n);
	
	long ans = comb.qpow(m, n);
	foreach(i; 0 .. m) {
		int sgn = ((m - i) & 1) ? -1 : 1;
		ans += sgn * comb.qpow(i, n) * comb.binom(m, i);
		ans %= P;
	}
	
	ans %= P;
	if(ans < 0) ans += P;
	writeln(ans);
}