N, M = map(int, input().split())
mod = 998244353
ans = 0

coef = [0] * (M + 1)
for i in range(1, M + 1):
    coef[i] = pow(i, N - 1, mod)

for i in range(1, M + 1):
    ans += i * (i*(i+1)//2 * coef[i] * N)
    ans -= i * (i*(i-1)//2 * coef[i-1] * N)
    ans += i * ((M*(M+1)//2-i*(i+1)//2) * coef[M-i] * N)
    ans -= i * ((M*(M+1)//2-i*(i-1)//2) * coef[M-i+1] * N)
    ans %= mod

print(ans)