#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using mint = modint998244353;

constexpr int FACT_SIZE = 10000;
mint Fact[FACT_SIZE + 1];
mint iFact[FACT_SIZE + 1];
const auto fact_init = [] {
    Fact[0] = mint::raw(1);
    for(int i = 1; i <= FACT_SIZE; ++i) {
        Fact[i] = Fact[i-1] * i;
    }
    iFact[FACT_SIZE] = Fact[FACT_SIZE].inv();
    for(int i = FACT_SIZE; i; --i) {
        iFact[i-1] = iFact[i] * i;
    }
    return false;
}();

mint comb(int n, int k) {
    if (k == 0) return mint::raw(1);
    assert(n >= 0 && k >= 0);
    if (k > n) return mint::raw(0);
    return Fact[n] * iFact[n - k] * iFact[k];
}

mint icomb(int n, int k) {
    return iFact[n] * Fact[n - k] * Fact[k];
}

mint fact(int n) {return Fact[n];}
mint perm(int n, int k) {
    assert(0 <= n);
    return Fact[n] * iFact[n - k];
}

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  VI a(n), b(n);
  rep(i, n) cin >> a[i];
  rep(i, n) cin >> b[i];
  constexpr int INF = 1001001001;
  deque<vector<mint>> q;
  int base = 0;
  rep(r, m) {
    int amn = INF, bmn = INF;
    for(int i = r; i < n; i += m) {
      chmin(amn, a[i]);
      chmin(bmn, b[i]);
    }
    int sz = amn + bmn + 1;
    vector<mint> f(sz, 1);
    for(int i = r; i < n; i += m) {
      int sm = a[i] + b[i];
      rep(j, sz) f[j] *= comb(sm, b[i] - bmn + j);
    }
    q.emplace_back(move(f));
    base += bmn;
  }
  while(q.size() >= 2) {
    auto f = move(q.front()); q.pop_front();
    auto g = move(q.front()); q.pop_front();
    q.emplace_back(convolution(f, g));
  }
  mint ans = q[0][base];
  cout << ans.val() << '\n';
}