import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
mod = 998244353
nn = 10**6
fact = [1] * nn
for i in range(nn - 1):
    fact[i + 1] = fact[i] * (i + 1) % mod
invfact = [1] * nn
invfact[nn - 1] = pow(fact[nn - 1], mod - 2, mod)
for i in range(nn - 1)[::-1]:
    invfact[i] = invfact[i + 1] * (i + 1) % mod
 
def binom(x, y):
    if x < 0 or y < 0 or x - y < 0:
        return 0
    return fact[x] * invfact[y] % mod * invfact[x - y] % mod

n, m = na()

a = na()
b = na()
f = []


LA = [0] * m
LB = [0] * m
for i in range(m):
    A = []
    B = []
    la = float("inf")
    lb = float("inf")
    for j in range(i, n, m):
        la = min(la, a[j])
        lb = min(lb, b[j])
    LB[i] = lb
    LA[i] = la
S = sum(LB)
dp = [0] * (S+1)
dp[0] = 1
for i in range(m):
    la,lb = LA[i],LB[i]
    op = [1] * (la+lb+1)
    for j in range(i, n, m):
        for k in range(-lb, la+1):
            op[k+lb] *= binom(a[j]+b[j],k+b[j])
            op[k+lb] %= mod
    ndp = [0] * (S+1)
    dp, ndp = ndp, dp
    for i in range(S+1):
        for j, x in enumerate(op):
            if j + i > S:
                break
            dp[j+i] += ndp[i] * x % mod
            dp[j+i] %= mod

print(dp[-1])