SIZE=100001; MOD=10**9+7 #998244353 #ここを変更する

SIZE += 1
inv = [0]*SIZE  # inv[j] = j^{-1} mod MOD
fac = [0]*SIZE  # fac[j] = j! mod MOD
finv = [0]*SIZE # finv[j] = (j!)^{-1} mod MOD
inv[1] = 1
fac[0] = fac[1] = 1
finv[0] = finv[1] = 1
for i in range(2,SIZE):
    inv[i] = MOD - (MOD//i)*inv[MOD%i]%MOD
    fac[i] = fac[i-1]*i%MOD
    finv[i]= finv[i-1]*inv[i]%MOD

def choose(n,r): # nCk mod MOD の計算
    if 0 <= r <= n:
        return (fac[n]*finv[r]%MOD)*finv[n-r]%MOD
    else:
        return 0

def chofuku(ball,box): # nHk mod MOD の計算
    return choose(box+ball-1,box)

# coding: utf-8
# Your code here!
import sys
readline = sys.stdin.readline
read = sys.stdin.read


n,m = [int(i) for i in read().split()]
ans = 0
x = 0
for i in range(n):
    v = choose(m,m-i)*pow(m-i,n,MOD)
    if x: ans -= v
    else: ans += v
    ans %= MOD    
    x ^= 1

print(ans)