import sys
input = sys.stdin.readline

N,M=map(int,input().split())
A=list(map(int,input().split()))
B=list(map(int,input().split()))

mod=998244353

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]%mod*FACT_INV[a-b]%mod
    else:
        return 0

PLUS=[[1]*601 for i in range(M)]

for i in range(N):
    k=i%M
    a=A[i]
    b=B[i]

    for j in range(601):
        p=j-300
        # bの方がaよりp多い

        score=0

        for x in range(a+1):
            y=x+p

            if 0<=y<=b:
                score+=Combi(a,x)*Combi(b,y)
                score%=mod
                
        PLUS[k][j]=PLUS[k][j]*score%mod

DP=[0]*(2*300*300+1)
DP[300*300]=1

for i in range(M):
    NDP=[0]*(2*300*300+1)

    for j in range(2*300*300+1):
        if DP[j]==0:
            continue
        for k in range(601):
            p=k-300

            if 0<=j+p<2*300*300:
                NDP[j+p]=(NDP[j+p]+DP[j]*PLUS[i][k])%mod
    DP=NDP

print(DP[300*300])