#!/usr/bin/env python3
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

MOD = 10**9 + 7

# %%
N, M = map(int, read().split())

# %%
fact = [1] * (M + 1)
for n in range(1, M + 1):
    fact[n] = fact[n - 1] * n % MOD
fact_inv = [1] * (M + 1)
fact_inv[M] = pow(fact[M], MOD - 2, MOD)
for n in range(M, 0, -1):
    fact_inv[n - 1] = fact_inv[n] * n % MOD


# %%
x = 0
for i in range(M):
    comb = fact[M] * fact_inv[i] * fact_inv[M - i] % MOD
    p = pow(M - i, N, MOD)
    x += (-1) ** i * comb * p
print(x % MOD)