n,m = map(int,input().split())
mod = 998244353
ans = 0
bef = 0
for i in range(1,m+1):
    all = i*(i+1)//2*pow(i,n-1,mod)*n%mod
    ans += i*(all-bef)
    ans %= mod
    bef = all
bef = 0
for i in range(m,0,-1):
    all = (m*(m+1)//2-i*(i-1)//2)*pow(m+1-i,n-1,mod)*n%mod
    ans -= i*(all-bef)
    ans %= mod
    bef = all  
print(ans)