// Problem: No.2230 Good Omen of White LotusNo.2230 白莲花吉兆
// Contest: yukicoder
// URL: https://yukicoder.me/problems/no/2230
// Memory Limit: 512 MB
// Time Limit: 2000 ms

#include <bits/stdc++.h>

#define fastio ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#define dbg(x) cout << #x << " = " << (x) << "\n";
#define popcount(x) __builtin_popcountll((x))
#define all(v) (v).begin(), (v).end()
#define pb emplace_back
#define x first
#define y second

using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;

const int inf = 0x3f3f3f3f;
const int mod = 998244353;

struct mint {
  ll x;  // typedef long long ll;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}
  mint operator-() const { return mint(-x); }
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod - a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint operator+(const mint a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= a;
  }
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1) a *= *this;
    return a;
  }

  // for prime mod
  mint inv() const { return pow(mod - 2); }
  mint& operator/=(const mint a) { return (*this) *= a.inv(); }
  mint operator/(const mint a) const {
    mint res(*this);
    return res /= a;
  }
};
istream& operator>>(istream& is, mint& a) { return is >> a.x; }
ostream& operator<<(ostream& os, const mint& a) { return os << a.x; }

int h, w, n, p;

void solve() {
  cin >> h >> w >> n >> p;
  vector<int> vx, vy;
  set<pll> vis;
  for (int i = 1; i <= n; i++) {
    int x, y;
    cin >> x >> y;
    vis.insert({x, y});
    vx.pb(x), vx.pb(x - 1), vx.pb(x + 1);
    vy.pb(y), vy.pb(y - 1), vy.pb(y + 1);
  }
  sort(all(vx));
  vx.erase(unique(all(vx)), vx.end());
  sort(all(vy));
  vy.erase(unique(all(vy)), vy.end());
  int nn = vx.size(), mm = vy.size();
  auto dp = vector<vector<int>>(nn, vector<int>(mm));
  for (int i = 0; i < nn; i++) {
    for (int j = 0; j < mm; j++) {
      if (i) dp[i][j] = max(dp[i - 1][j], dp[i][j]);
      if (j) dp[i][j] = max(dp[i][j - 1], dp[i][j]);
      if (vis.count({vx[i], vy[j]})) dp[i][j]++;
    }
  }
  mint sum(h + w - 3);
  mint cnt(dp[nn - 1][mm - 1]);
  mint ans = mint(1) - mint(2) * mint(p).inv();
  ans = ans.pow(cnt.x);
  ans = ans * (mint(1) - mint(p).inv()).pow((sum - cnt).x);

  cout << mint(1) - ans << "\n";
}

int main() {
  fastio;
  int t = 1;
  // cin >> t;
  while (t--) {
    solve();
  }
  return 0;
}