import sys
readline = sys.stdin.readline

N, M = map(int, input().split())
mod = 10**9 + 7
fac, inv = [1]*(M+1), [0]*(M+1)
for i in range(2, M+1):
    fac[i] = fac[i-1] * i % mod
inv[-1] = pow(fac[-1], mod-2, mod)
for i in range(M, 0, -1):
    inv[i-1] = inv[i] * i % mod

ans = 0
for i in range(M+1):
    ans += fac[M] * inv[i] * inv[M-i] * \
        pow(M-i, N, mod) * (-1 if i & 1 else 1) % mod

print(ans % mod)