N,M=map(int,input().split())
mod=10**9+7

FACT=[1]
for i in range(1,2*10**5+1):
    FACT.append(FACT[-1]*i%mod)

FACT_INV=[pow(FACT[-1],mod-2,mod)]
for i in range(2*10**5,0,-1):
    FACT_INV.append(FACT_INV[-1]*i%mod)

FACT_INV.reverse()

def Combi(a,b):
    if 0<=b<=a:
        return FACT[a]*FACT_INV[b]*FACT_INV[a-b]%mod
    else:
        return 0

ANS=0
for i in range(N):
    ANS+=(-1)**i*Combi(M,i)*pow(M-i,N,mod)
    ANS%=mod
print(ANS)